United States

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United States

United States of America

CAPITAL: Washington, D.C. (District of Columbia).

FLAG: The flag consists of 13 alternate stripes, 7 red and 6 white; these represent the 13 original colonies. Fifty 5-pointed white stars, representing the present number of states in the Union, are placed in 9 horizontal rows alternately of 6 and 5 against a blue field in the upper left corner of the flag.

OFFICIAL SEAL: Obverse: An American eagle with outstretched wings bears a shield consisting of 13 alternating white and red stripes with a broad blue band across the top. The right talon clutches an olive branch, representing peace; in the left are 13 arrows, symbolizing military strength. The eagle's beak holds a banner with the motto "E pluribus unum" (From many, one); overhead is a constellation of 13 five-pointed stars in a glory. Reverse: Above a truncated pyramid is an all-seeing eye within a triangle; at the bottom of this triangle appear the roman numerals MDCCLXXVI (1776). The pyramid stands on a grassy ground, against a backdrop of mountains. The words "Annuit Coeptis" (He has favored our undertakings) and, on a banner, "Novus Ordo Seclorum" (A new order of the ages) surround the whole.

ANTHEM: The Star-Spangled Banner.

MOTTO: In God We Trust.

MONETARY UNIT: The dollar ($) of 100 cents is a paper currency with a floating rate. There are coins of 1, 5, 10, 25, and 50 cents and 1 dollar, and notes of 1, 2, 5, 10, 20, 50, and 100 dollars. Although issuance of higher notes ceased in 1969, a limited number of notes of 500, 1,000, 5,000, and 10,000 dollars remain in circulation. A gold-colored 1 dollar coin featuring Sacagawea was introduced in 2000.

WEIGHTS AND MEASURES: The imperial system is in common use; however, the use of metrics in industry is increasing, and the metric system is taught in public schools throughout the United States. Common avoirdupois units in use are the avoirdupois pound of 16 oz or 453.5924277 gm; the long ton of 2,240 lb or 35,840 oz; and the short ton, more commonly used, of 2,000 lb or 32,000 oz. (Unless otherwise indicated, all measures given in tons are in short tons.) Liquid measures: 1 gallon = 231 cu in = 4 quarts = 8 pints. Dry measures: 1 bushel = 4 pecks = 32 dry quarts = 64 dry pints. Linear measures: 1 ft = 12 in; 1 statute mi = 1,760 yd = 5,280 ft. Metric equivalent: 1 m = 39.37 in.

FEDERAL HOLIDAYS: New Year's Day, 1 January; Birthday of Martin Luther King, Jr., 3rd Monday in January; Lincoln's Birthday, 12 February (only in the northern and western states); Washington's Birthday, 3rd Monday in February; Memorial or Decoration Day, last Monday in May; Independence Day, 4 July; Labor Day, 1st Monday in September; Columbus Day, 2nd Monday in October; Election Day, 1st Tuesday after the 1st Monday in November; Veterans or Armistice Day, 11 November; Thanksgiving Day, 4th Thursday in November; Christmas, 25 December.

TIME: Eastern, 7 am = noon GMT; Central, 6 am = noon GMT; Mountain, 5 am = noon GMT; Pacific (includes the Alaska panhandle), 4 am = noon GMT; Yukon, 3 am = noon GMT; Alaska and Hawaii, 2 am = noon GMT; western Alaska, 1 am = noon GMT.


Located in the Western Hemisphere on the continent of North America, the United States is the fourth-largest country in the world. Its total area, including Alaska and Hawaii, is 9,629,091 sq km (3,717,813 sq mi). The conterminous United States extends 4,662 km (2,897 mi) enewsw and 4,583 km (2,848 mi) sse-nnw. It is bordered on the n by Canada, on the e by the Atlantic Ocean, on the s by the Gulf of Mexico and Mexico, and on the w by the Pacific Ocean, with a total boundary length of 17,563 km (10,913 mi). Alaska, the 49th state, extends 3,639 km (2,261 mi) e-w and 2,185 km (1,358 mi) n-s. It is bounded on the n by the Arctic Ocean and Beaufort Sea, on the e by Canada, on the s by the Gulf of Alaska, Pacific Ocean and Bering Sea, and on the w by the Bering Sea, Bering Strait, Chukchi Sea, and Arctic Ocean, with a total land boundary of 12,034 km (7,593 mi) and a coastline of 19,924 km (12,380 mi). The 50th state, Hawaii, consists of islands in the Pacific Ocean extending 2,536 km (1,576 mi) n-s and 2,293 km (1,425 mi) e-w, with a general coastline of 1,207 km (750 mi).

The nation's capital, Washington, D.C., is located on the mid-Atlantic coast.


Although the northern New England coast is rocky, along the rest of the eastern seaboard the Atlantic Coastal Plain rises gradually from the shoreline. Narrow in the north, the plain widens to about 320 km (200 mi) in the south and in Georgia merges with the Gulf Coastal Plain that borders the Gulf of Mexico and extends through Mexico as far as the Yucatán. West of the Atlantic Coastal Plain is the Piedmont Plateau, bounded by the Appalachian Mountains. The Appalachians, which extend from southwest Maine into central Alabamawith special names in some areasare old mountains, largely eroded away, with rounded contours and forested, as a rule, to the top. Few of their summits rise much above 1,100 m (3,500 ft), although the highest, Mt. Mitchell in North Carolina, reaches 2,037 m (6,684 ft).

Between the Appalachians and the Rocky Mountains, more than 1,600 km (1,000 mi) to the west, lies the vast interior plain of the United States. Running south through the center of this plain and draining almost two-thirds of the area of the continental United States is the Mississippi River. Waters starting from the source of the Missouri, the longest of its tributaries, travel almost 6,450 km (4,000 mi) to the Gulf of Mexico.

The eastern reaches of the great interior plain are bounded on the north by the Great Lakes, which are thought to contain about half the world's total supply of fresh water. Under US jurisdiction are 57,441 sq km (22,178 sq mi) of Lake Michigan, 54,696 sq km (21,118 sq mi) of Lake Superior, 23,245 sq km (8,975 sq mi) of Lake Huron, 12,955 sq km (5,002 sq mi) of Lake Erie, and 7,855 sq km (3,033 sq mi) of Lake Ontario. The five lakes are now accessible to oceangoing vessels from the Atlantic via the St. Lawrence Seaway. The basins of the Great Lakes were formed by the glacial ice cap that moved down over large parts of North America some 25,000 years ago. The glaciers also determined the direction of flow of the Missouri River and, it is believed, were responsible for carrying soil from what is now Canada down into the central agricultural basin of the United States.

The great interior plain consists of two major subregions: the fertile Central Plains, extending from the Appalachian highlands to a line drawn approximately 480 km (300 mi) west of the Mississippi, broken by the Ozark Plateau; and the more arid Great Plains, extending from that line to the foothills of the Rocky Mountains. Although they appear flat, the Great Plains rise gradually from about 460 m (1,500 ft) to more than 1,500 m (5,000 ft) at their western extremity.

The Continental Divide, the Atlantic-Pacific watershed, runs along the crest of the Rocky Mountains. The Rockies and the ranges to the west are parts of the great system of young, rugged mountains, shaped like a gigantic spinal column, that runs along western North, Central, and South America from Alaska to Tierra del Fuego, Chile. In the continental United States, the series of western ranges, most of them paralleling the Pacific coast, are the Sierra Nevada, the Coast Ranges, the Cascade Range, and the Tehachapi and San Bernardino mountains. Between the Rockies and the Sierra Nevada-Cascade mountain barrier to the west lies the Great Basin, a group of vast arid plateaus containing most of the desert areas of the United States, in the south eroded by deep canyons.

The coastal plains along the Pacific are narrow, and in many places the mountains plunge directly into the sea. The most extensive lowland near the west coast is the Great Valley of California, lying between the Sierra Nevada and the Coast Ranges. There are 71 peaks in these western ranges of the continental United States that rise to an altitude of 4,267 m (14,000 ft) or more, Mt. Whitney in California at 4,418 m (14,494 ft) being the highest. The greatest rivers of the Far West are the Colorado in the south, flowing into the Gulf of California, and the Columbia in the northwest, flowing to the Pacific. Each is more than 1,900 km (1,200 mi) long; both have been intensively developed to generate electric power, and both are important sources of irrigation.

Separated from the continental United States by Canadian territory, the state of Alaska occupies the extreme northwest portion of the North American continent. A series of precipitous mountain ranges separates the heavily indented Pacific coast on the south from Alaska's broad central basin, through which the Yukon River flows from Canada in the east to the Bering Sea in the west. The central basin is bounded on the north by the Brooks Range, which slopes down gradually to the Arctic Ocean. The Alaskan Peninsula and the Aleutian Islands, sweeping west far out to sea, consist of a chain of volcanoes, many still active.

The state of Hawaii consists of a group of Pacific islands formed by volcanoes rising sharply from the ocean floor. The highest of these volcanoes, Mauna Loa, at 4,168 m (13,675 ft), is located on the largest of the islands, Hawaii, and is still active.

The lowest point in the United States is Death Valley in California, 86 m (282 ft) below sea level. At 6,194 m (20,320 ft), Mt. McKinley in Alaska is the highest peak in North America. These topographic extremes suggest the geological instability of the Pacific Coast region, which is part of the "Ring of Fire," a seismically active band surrounding the Pacific Ocean. Major earthquakes destroyed San Francisco in 1906 and Anchorage, Alaska, in 1964, and the San Andreas Fault in California still causes frequent earth tremors. In 2004, there was a total of 3550 U.S. earthquakes documented by the United States Geological Survey National Earthquake Information Center. Washington State's Mt. St. Helens erupted in 1980, spewing volcanic ash over much of the Northwest.


The eastern continental region is well watered, with annual rainfall generally in excess of 100 cm (40 in). It includes all of the Atlantic seaboard and southeastern states and extends west to cover Indiana, southern Illinois, most of Missouri, Arkansas, Louisiana, and easternmost Texas. The eastern seaboard is affected primarily by the masses of air moving from west to east across the continent rather than by air moving in from the Atlantic. Hence its climate is basically continental rather than maritime. The midwestern and Atlantic seaboard states experience hot summers and cold winters; spring and autumn are clearly defined periods of climatic transition. Only Florida, with the Gulf of Mexico lying to its west, experiences moderate differences between summer and winter temperatures. Mean annual temperatures vary considerably between north and south: Boston, 11°c (51°f); New York City, 13°c (55°f); Charlotte, N.C., 16°c (61°f); Miami, Fla., 24°c (76°f).

The Gulf and South Atlantic states are often hit by severe tropical storms originating in the Caribbean in late summer and early autumn. In the past few years, the number of hurricanes and their severity have measurably increased. From 197094, there were about three hurricanes per year. From 1995 to 2003, there were a total of 32 major hurricanes with sustained winds of 111 miles per hour or greater.

In 2005 there were a record-breaking 23 named Atlantic hurricanes, three of which caused severe damage to the Gulf Coast region. On 25 August 2005, Hurricane Katrina hit Florida as a category 1 hurricane. By 29 August, the storm developed into a category 4 hurricane that made landfall in southern Louisiana. Several levees protecting the low-lying city of New Orleans broke, flooding the entire region under waters that rose over the rooftops of homes. Over 1,000 were killed by the storm. Over 500,000 people were left homeless and without jobs.

One month later, Hurricane Rita swept first into Florida and continued to make landfall between Sabine Pass, Texas, and Johnson's Bayou, Louisiana, on 24 September 2005 as a category 3 hurricane. Before reaching land, however, the storm had peaked as a category 5 hurricane that was placed on record as the strongest measured hurricane to ever have entered the Gulf of Mexico and the fourth most intense hurricane ever in the Atlantic Basin. Over 100 people were killed.

Hurricane Wilma followed on 24 October when it made landfall north of Everglades City in Florida as a category 3 hurricane. There were about 22 deaths in the United States from Wilma; however, the storm also hit Cuba, Haiti, Jamaica, and Mexico, reaching a death toll of at least 25 people from those countries combined.

The prairie lands lying to the west constitute a subhumid region. Precipitation usually exceeds evaporation by only a small amount; hence the region experiences drought more often than excessive rainfall. Dryness generally increases from east to west. The average midwinter temperature in the extreme northMinnesota and North Dakotais about 13°c (9°f) or less, while the average July temperature is 18°c (65 °f). In the Texas prairie region to the south, January temperatures average 10-13°c (50-55 °f) and July temperatures 27-29°c (80-85 °f). Rainfall along the western border of the prairie region is as low as 46 cm (18 in) per year in the north and 64 cm (25 in) in the south. Precipitation is greatest in the early summera matter of great importance to agriculture, particularly in the growing of grain crops. In dry years, the prevailing winds may carry the topsoil eastward (particularly from the southern region) for hundreds of miles in clouds that obscure the sun.

The Great Plains constitute a semiarid climatic region. Rainfall in the southern plains averages about 50 cm (20 in) per year and in the northern plains about 25 cm (10 in), but extreme year-to-year variations are common. The tropical air masses that move northward across the plains originate on the fairly high plateaus of Mexico and contain little water vapor. Periods as long as 120 days without rain have been experienced in this region. The rains that do occur are often violent, and a third of the total annual rainfall may be recorded in a single day at certain weather stations. The contrast between summer and winter temperatures is extreme throughout the Great Plains. Maximum summer temperatures of over 43°c (110°f) have been recorded in the northern as well as in the southern plains. From the Texas panhandle north, blizzards are common in the winter, and tornadoes at other seasons. The average minimum temperature for January in Duluth, Minn., is 19°c (3 °f).

The higher reaches of the Rockies and the mountains paralleling the Pacific coast to the west are characterized by a typical alpine climate. Precipitation as a rule is heavier on the western slopes of the ranges. The great intermontane arid region of the West shows

United StatesOutlying Areas of the United States1
1Excludes minor and uninhabited islands.
2Although governed under separate constitutional arrangements by the mid-1980s, these territories formally remained part of the Trust Territory of the Pacific Islands pending action by the US Congress, the US president, and the UN Security Council.
3Centers of constitutional government. The entire Trust Territory of the Pacific Islands is administered from Saipan.
Puerto Rico3,5159,104San Juan18983,196,5203,887,652
Virgin Islands of the United States136352Charlotte Amalie191796,569119,827
Trust Territory of the Pacific Islands, of which:7131,847Saipan1947132,92987,865
  Northern Marianas2182471Saipan3-16,78069,398
  Republic of Palau2191495Koror3-12,11618,467
Other Pacific territories:
  American Samoa77199Pago Pago189932,29763,786
  Midway Islands25-1867468n.a.
  Wake Island38-1899302n.a.

considerable climatic variation between its northern and southern portions. In New Mexico, Arizona, and southeastern California, the greatest precipitation occurs in July, August, and September, mean annual rainfall ranging from 8 cm (3 in) in Yuma, Ariz., to 76 cm (30 in) in the mountains of northern Arizona and New Mexico. Phoenix has a mean annual temperature of 22°c (71°f), rising to 33°c (92°f) in July and falling to 11°c (52°f) in January. North of the Utah-Arizona line, the summer months usually are very dry; maximum precipitation occurs in the winter and early spring. In the desert valleys west of Great Salt Lake, mean annual precipitation adds up to only 10 cm (4 in). Although the northern plateaus are generally arid, some of the mountainous areas of central Washington and Idaho receive at least 152 cm (60 in) of rain per year. Throughout the intermontane region, the uneven availability of water is the principal factor shaping the habitat.

The Pacific coast, separated by tall mountain barriers from the severe continental climate to the east, is a region of mild winters and moderately warm, dry summers. Its climate is basically maritime, the westerly winds from the Pacific Ocean moderating the extremes of both winter and summer temperatures. Los Angeles in the south has an average temperature of 13°c (56 °f) in January and 21°c (69°f) in July; Seattle in the north has an average temperature of 4°c (39°f) in January and 18°c (65°f) in July. Precipitation in general increases along the coast from south to north, extremes ranging from an annual average of 4.52 cm (1.78 in) at Death Valley in California (the lowest in the United States) to more than 356 cm (140 in) in Washington's Olympic Mountains.

Climatic conditions vary considerably in the vastness of Alaska. In the fogbound Aleutians and in the coastal panhandle strip that extends southeastward along the Gulf of Alaska and includes the capital, Juneau, a relatively moderate maritime climate prevails. The interior is characterized by short, hot summers and long, bitterly cold winters, and in the region bordering the Arctic Ocean a polar climate prevails, the soil hundreds of feet below the surface remaining frozen the year round. Although snowy in winter, continental Alaska is relatively dry.

Hawaii has a remarkably mild and stable climate with only slight seasonal variations in temperature, as a result of northeast ocean winds. The mean January temperature in Honolulu is 23°c (73 °f); the mean July temperature 27°c (80°f). Rainfall is moderateabout 71 cm (28 in) per yearbut much greater in the mountains; Mt. Waialeale on Kauai has a mean annual rainfall of 1,168 cm (460 in), highest in the world.

The lowest temperature recorded in the United States was 62°c (79.8°f) at Prospect Creek Camp, Alaska, on 23 January 1971; the highest, 57°c (134°f) at Greenland Ranch, in Death Valley, Calif., on 10 July 1913. The record annual rainfall is 1,878 cm (739 in) recorded at Kukui, Maui in 1982; the previous record for a one-year period was 1,468 cm (578 in) recorded at Fuu Kukui, Maui, in 1950; in 1 hour, 30 cm (12 in), at Holt, Mo., on 22 June 1947, and on Kauai, Hawaii, on 24-25 January 1956.


At least 7,000 species and subspecies of indigenous US flora have been categorized. The eastern forests contain a mixture of softwoods and hardwoods that includes pine, oak, maple, spruce, beech, birch, hemlock, walnut, gum, and hickory. The central hardwood forest, which originally stretched unbroken from Cape Cod to Texas and northwest to Minnesotastill an important timber sourcesupports oak, hickory, ash, maple, and walnut. Pine, hickory, tupelo, pecan, gum, birch, and sycamore are found in the southern forest that stretches along the Gulf coast into the eastern half of Texas. The Pacific forest is the most spectacular of all because of its enormous redwoods and Douglas firs. In the southwest are saguaro (giant cactus), yucca, candlewood, and the Joshua tree.

The central grasslands lie in the interior of the continent, where the moisture is not sufficient to support the growth of large forests. The tall grassland or prairie (now almost entirely under cultivation) lies to the east of the 100th meridian. To the west of this line, where rainfall is frequently less than 50 cm (20 in) per year, is the short grassland. Mesquite grass covers parts of west Texas, southern New Mexico, and Arizona. Short grass may be found in the highlands of the latter two states, while tall grass covers large portions of the coastal regions of Texas and Louisiana and occurs in some parts of Mississippi, Alabama, and Florida. The Pacific grassland includes northern Idaho, the higher plateaus of eastern Washington and Oregon, and the mountain valleys of California.

The intermontane region of the Western Cordillera is for the most part covered with desert shrubs. Sagebrush predominates in the northern part of this area, creosote in the southern, with salt-brush near the Great Salt Lake and in Death Valley.

The lower slopes of the mountains running up to the coastline of Alaska are covered with coniferous forests as far north as the Seward Peninsula. The central part of the Yukon Basin is also a region of softwood forests. The rest of Alaska is heath or tundra. Hawaii has extensive forests of bamboo and ferns. Sugarcane and pineapple, although not native to the islands, now cover a large portion of the cultivated land.

Small trees and shrubs common to most of the United States include hackberry, hawthorn, serviceberry, blackberry, wild cherry, dogwood, and snowberry. Wildflowers bloom in all areas, from the seldom-seen blossoms of rare desert cacti to the hardiest alpine species. Wildflowers include forget-me-not, fringed and closed gentians, jack-in-the-pulpit, black-eyed Susan, columbine, and common dandelion, along with numerous varieties of aster, orchid, lady's slipper, and wild rose.

An estimated 428 species of mammals characterize the animal life of the continental United States. Among the larger game animals are the white-tailed deer, moose, pronghorn antelope, bighorn sheep, mountain goat, black bear, and grizzly bear. The Alaskan brown bear often reaches a weight of 1,200-1,400 lbs. Some 25 important furbearers are common, including the muskrat, red and gray foxes, mink, raccoon, beaver, opossum, striped skunk, wood-chuck, common cottontail, snowshoe hare, and various squirrels. Human encroachment has transformed the mammalian habitat over the last two centuries. The American buffalo (bison), millions of which once roamed the plains, is now found only on select reserves. Other mammals, such as the elk and gray wolf, have been restricted to much smaller ranges.

Year-round and migratory birds abound. Loons, wild ducks, and wild geese are found in lake country; terns, gulls, sandpipers, herons, and other seabirds live along the coasts. Wrens, thrushes, owls, hummingbirds, sparrows, woodpeckers, swallows, chickadees, vireos, warblers, and finches appear in profusion, along with the robin, common crow, cardinal, Baltimore oriole, eastern and western meadowlarks, and various blackbirds. Wild turkey, ruffed grouse, and ring-necked pheasant (introduced from Europe) are popular game birds. There are at least 508 species of birds found throughout the country.

Lakes, rivers, and streams teem with trout, bass, perch, muskellunge, carp, catfish, and pike; sea bass, cod, snapper, and flounder are abundant along the coasts, along with such shellfish as lobster, shrimp, clams, oysters, and mussels. Garter, pine, and milk snakes are found in most regions. Four poisonous snakes survive, of which the rattlesnake is the most common. Alligators appear in southern waterways and the Gila monster makes its home in the Southwest.

Laws and lists designed to protect threatened and endangered flora and fauna have been adopted throughout the United States. Generally, each species listed as protected by the federal government is also protected by the states, but some states may list species not included on federal lists or on the lists of neighboring states. (Conversely, a species threatened throughout most of the United States may be abundant in one or two states.) As of November 2005, the US Fish and Wildlife Service listed 997 endangered US species (up from 751 listed in 1996), including 68 species of mammals, 77 birds, 74 fish, and 599 plants; and 275 threatened species (209 in 1996), including 11 species of mammals, 13 birds, 42 fish, and 146 plants. The agency listed another 520 endangered and 46 threatened foreign species by international agreement.

Threatened species, likely to become endangered if recent trends continue, include such plants as Lee pincushion cactus. Among the endangered floral species (in imminent danger of extinction in the wild) are the Virginia round-leaf birch, San Clemente Island broom, Texas wildrice, Furbish lousewort, Truckee barberry, Sneed pincushion cactus, spineless hedgehog cactus, Knowlton cactus, persistent trillium, dwarf bear-poppy, and small whorled pogonia.

Endangered mammals included the red wolf, black-footed ferret, jaguar, key deer, northern swift fox, San Joaquin kit fox, jaguar, jaguarundi, Florida manatee, ocelot, Florida panther, Utah prairie dog, Sonoran pronghorn, and numerous whale species. Endangered species of rodents included the Delmarva Peninsula fox squirrel, beach mouse, salt-marsh harvest mouse, 7 species of bat (Virginia and Ozark big-eared Sanborn's and Mexican long-nosed, Hawaiian hoary, Indiana, and gray), and the Morro Ba, Fresno, Stephens', and Tipton Kangaroo rats and rice rat.

Endangered species of birds included the California condor, bald eagle, three species of falcon (American peregrine, tundra peregrine, and northern aplomado), Eskimo curlew, two species of crane (whooping and Mississippi sandhill), three species of warbler (Kirtland's, Bachman's, and golden-cheeked), dusky seaside sparrow, light-footed clapper rail, least tern, San Clemente loggerhead shrike, bald eagle (endangered in most states, but only threatened in the Northwest and the Great Lakes region), Hawaii creeper, Everglade kite, California clapper rail, and red-cockaded woodpecker. Endangered amphibians included four species of salamander (Santa Cruz long-toed, Shenandoah, desert slender, and Texas blind), Houston and Wyoming toad, and six species of turtle (green sea, hawksbill, Kemp's ridley, Plymouth and Alabama redbellied, and leatherback). Endangered reptiles included the American crocodile, (blunt nosed leopard and island night), and San Francisco garter snake.

Aquatic species included the shortnose sturgeon, Gila trout, eight species of chub (humpback, Pahranagat, Yaqui, Mohave tui, Owens tui, bonytail, Virgin River, and Borax lake), Colorado River squawfish, five species of dace (Kendall Warm Springs, and Clover Valley, Independence Valley, Moapa and Ash Meadows speckled), Modoc sucker, cui-ui, Smoky and Scioto madtom, seven species of pupfish (Leon Springs, Gila Desert, Ash Meadows Amargosa, Warm Springs, Owens, Devil's Hole, and Comanche Springs), Pahrump killifish, four species of gambusia (San Marcos, Pecos, Amistad, Big Bend, and Clear Creek), six species of darter (fountain, watercress, Okaloosa, boulder, Maryland, and amber), totoaba, and 32 species of mussel and pearly mussel. Also classified as endangered were two species of earthworm (Washington giant and Oregon giant), the Socorro isopod, San Francisco forktail damselfly, Ohio emerald dragonfly, three species of beetle (Kretschmarr Cave, Tooth Cave, and giant carrion), Belkin's dune tabanid fly, and 10 species of butterfly (Schaus' swallowtail, lotis, mission, El Segundo, and Palos Verde blue, Mitchell's satyr, Uncompahgre fritillary, Lange's metalmark, San Bruno elfin, and Smith's blue).

Endangered plants in the United States include: aster, cactus, pea, mustard, mint, mallow, bellflower and pink family, snapdragon, and buckwheat. Several species on the federal list of endangered and threatened wildlife and plants are found only in Hawaii. Endangered bird species in Hawaii included the Hawaiian dark-rumped petrel, Hawaiian gallinule, Hawaiian crow, three species of thrush (Kauai, Molokai, and puaiohi), Kauai 'o'o, Kauai nukupu'u, Kauai 'alialoa, 'akiapola'au, Maui'akepa, Molokai creeper, Oahu creeper, palila, and 'o'u.

Species formerly listed as threatened or endangered that have been removed from the list include (with delisting year and reason) American alligator (1987, recovered); coastal cutthroat trout (2000, taxonomic revision); Bahama swallowtail butterfly (1984, amendment); gray whale (1994, recovered); brown pelican (1984, recovered); Rydberg milk-vetch (1987, new information); Lloyd's hedgehog cactus (1999, taxonomic revision), and Columbian white-tailed Douglas County Deer (2003, recovered).

There are at least 250 species of plants and animals that have become extinct, including the Wyoming toad, the Central Valley grasshopper, Labrador duck, Carolina parakeet, Hawaiian crow, chestnut moth, and the Franklin tree.


The Council on Environmental Quality, an advisory body contained within the Executive Office of the President, was established by the National Environmental Policy Act of 1969, which mandated an assessment of environmental impact for every federally funded project. The Environmental Protection Agency (EPA), created in 1970, is an independent body with primary regulatory responsibility in the fields of air and noise pollution, water and waste management, and control of toxic substances. Other federal agencies with environmental responsibilities are the Forest Service and Soil Conservation Service within the Department of Agriculture, the Fish and Wildlife Service and the National Park Service within the Department of the Interior, the Department of Energy, and the Nuclear Regulatory Commission. In addition to the 1969 legislation, landmark federal laws protecting the environment include the Clean Air Act Amendments of 1970 and 1990, controlling automobile and electric utility emissions; the Water Pollution Act of 1972, setting clean-water criteria for fishing and swimming; and the Endangered Species Act of 1973, protecting wildlife near extinction.

A measure enacted in December 1980 established a $1.6-billion "Superfund," financed largely by excise taxes on chemical companies, to clean up toxic waste dumps such as the one in the Love Canal district of Niagara Falls, N.Y. In 2005, there were 1,238 hazardous waste sites on the Superfund's national priority list.

The most influential environmental lobbies include the Sierra Club (founded in 1892; 700,000 members in 2003) and its legal arm, the Sierra Club Legal Defense Fund. Large conservation groups include the National Wildlife Federation (1936; over 4,000,000), the National Audubon Society (1905; 600,000), and the Nature Conservancy (1917; 1,000,000). Greenpeace USA (founded in 1979) has gained international attention by seeking to disrupt hunts for whales and seals.

Among the environmental movement's most notable successes have been the inauguration (and mandating in some states) of recycling programs; the banning in the United States of the insecticide dichlorodiphenyltrichloroethane (DDT); the successful fight against construction of a supersonic transport (SST); and the protection of more than 40 million hectares (100 million acres) of Alaska lands (after a fruitless fight to halt construction of the trans-Alaska pipeline); and the gradual elimination of chlorofluorocarbon (CFC) production by 2000. In March 2003, the US Senate narrowly voted to reject a Bush administration plan to begin oil exploration in the 19 million acre (7.7 million hectare) Arctic National Wildlife Refuge (ANWR). In 2003, about 25.9% of the total land area was protected. The United States has 12 natural UNESCO World Heritage Sites and 22 Ramsar wetland sites. Yellowstone National Park, founded in 1872, was the first national park established worldwide.

Outstanding problems include acid rain (precipitation contaminated by fossil fuel wastes); inadequate facilities for solid waste disposal; air pollution from industrial emissions (the United States leads the world in carbon dioxide emissions from the burning of fossil fuels); the contamination of homes by radon, a radio

United StatesState Areas, Entry Dates, and Populations
Census closest to entry date.
Date fixed in 1953 by congressional resolution.
*One of original 13 colonies.
Alabama51,705133,91619Montgomery2214 December 1819127,9014,040,5874,447,100
Alaska591,0041,530,6991Juneau493 January 1959226,167550,043626,932
Arizona114,000295,2606Phoenix4814 February 1912204,3543,665,2285,130,632
Arkansas53,187137,75427Little Rock2515 June 183657,5742,350,7252,673,400
California158,706411,0483Sacramento319 September 185092,59729,760,02133,871,648
Colorado104,091269,5958Denver381 August 187639,8643,294,3944,301,261
Connecticut*5,01812,99748Hartford59 January 1788237,9463,287,1163,405,565
Delaware*2,0445,29449Dover17 December 178759,096666,168783,600
Florida58,664151,94022Tallahassee273 March 184587,44512,937,92615,982,378
Georgia*58,910152,57721Atlanta42 January 178882,5486,478,3168,186,453
Hawaii6,47116,76047Honolulu5021 August 1959632,7721,108,2291,211,537
Idaho83,564216,43113Boise433 July 189088,5481,006,7491,293,953
Illinois56,345145,93324Springfield213 December 181855,21111,430,60212,419,293
Indiana36,18593,71938Indianapolis1911 December 1816147,1785,544,1596,080,485
Iowa56,275145,75225Des Moines2928 December 1846192,2142,776,7552,926,324
Kansas82,277213,09714Topeka3429 January 1861107,2062,477,5742,688,418
Kentucky40,409104,65937Frankfort151 June 179273,6773,685,2964,041,769
Louisiana47,752123,67831Baton Rouge1830 April 181276,5564,219,9734,468,976
Maine33,26586,15639Augusta2315 March 1820298,3351,227,9281,274,923
Maryland*10,46027,09142Annapolis728 April 1788319,7284,781,4685,296,486
Massachusetts*8,28421,45645Boston66 February 1788378,7876,016,4256,349,097
Michigan58,527151,58523Lansing2626 January 1837212,2679,295,2979,938,444
Minnesota84,402218,60112St. Paul3211 May 1858172,0234,375,0994,919,497
Mississippi47,689123,51432Jackson2010 December 181775,4482,573,2162,844,658
Missouri69,697180,51519Jefferson City2410 August 182166,5865,117,0735,595,211
Montana147,046380,8494Helena418 November 1889142,924799,065902,195
Nebraska77,355200,34915Lincoln371 March 1867122,9931,578,3851,711,263
Nevada110,561286,3537Carson City3631 October 186442,4911,201,8331,998,257
New Hampshire*9,27924,03344Concord921 June 1788141,8851,109,2521,235,786
New Jersey*7,78720,16846Trenton318 December 1787184,1397,730,1888,414,350
New Mexico121,593314,9265Santa Fe476 January 1912327,3011,515,0691,819,046
New York*49,108127,19030Albany1126 July 1788340,12017,990,45518,976,457
North Carolina*52,669136,41328Raleigh1221 November 1789393,7516,628,6378,049,313
North Dakota70,702183,11817Bismarck392 November 1889190,983638,800642,200
Ohio41,330107,04535Columbus171 March 180343,36510,847,11511,353,140
Oklahoma69,956181,18618Oklahoma City4616 November 1907657,1553,145,5853,450,654
Oregon97,073251,41910Salem3314 February 185952,4652,842,3213,421,399
Pennsylvania*45,308117,34833Harrisburg212 December 1787434,37311,003,46412,281,054
Rhode Island*1,2123,13950Providence1329 May 179068,8251,003,4641,048,319
South Carolina*31,11380,58340Columbia823 May 1788393,7513,486,7034,012,012
South Dakota77,116199,73016Pierre402 November 1889348,600696,004754,844
Tennessee42,144109,15334Nashville161 June 179635,6914,877,1855,689,283
Texas266,807691,0302Austin2829 December 1845212,59216,986,51020,851,820
Utah84,899219,88811Salt Lake City454 January 1896276,7491,722,8502,233,169
Vermont9,61424,90043Montpelier144 March 179185,425562,758608,827
Virginia*40,767105,58636Richmond1025 June 1788747,6106,187,3587,078,515
Washington68,139176,48020Olympia4211 November 1889357,2324,866,6925,894,121
West Virginia24,23162,75841Charleston3520 June 1863442,0141,793,4771,808,344
Wisconsin56,153145,43626Madison3029 May 1848305,3914,891,7695,363,675
Wyoming97,809253,3259Cheyenne4410 July 189062,555453,588493,782

active gas that is produced by the decay of underground deposits of radium and can cause cancer; runoffs of agricultural pesticides, pollutants deadly to fishing streams and very difficult to regulate; continued dumping of raw or partially treated sewage from major cities into US waterways; falling water tables in many western states; the decrease in arable land because of depletion, erosion, and urbanization; the need for reclamation of strip-mined lands and for regulation of present and future strip mining; and the expansion of the US nuclear industry in the absence of a fully satisfactory technique for the handling and permanent disposal of radioactive wastes.


The population of United States in 2005 was estimated by the United Nations (UN) at 296,483,000, which placed it at number 3 in population among the 193 nations of the world. In 2005, approximately 12% of the population was over 65 years of age, with another 21% of the population under 15 years of age. There were 97 males for every 100 females in the country. According to the UN, the annual population rate of change for 20052010 was expected to be 0.6%, a rate the government viewed as satisfactory. The projected population for the year 2025 was 349,419,000. The population density was 207 per sq km (80 per sq mi), with major population concentrations are along the northeast Atlantic coast and the southwest Pacific coast. The population is most dense between New York City and Washington, D.C.

At the time of the first federal census, in 1790, the population of the United States was 3,929,214. Between 1800 and 1850, the population almost quadrupled; between 1850 and 1900, it tripled; and between 1900 and 1950, it almost doubled. During the 1960s and 1970s, however, the growth rate slowed steadily, declining from 2.9% annually in 1960 to 2% in 1969 and to less than 1% from the 1980s through 2000. The population has aged: the median age of the population increased from 16.7 years in 1820 to 22.9 years in 1900 and to 34.3 years in 1995.

Suburbs have absorbed most of the shift in population distribution since 1950. The UN estimated that 79% of the population lived in urban areas in 2005, and that urban areas were growing at an annual rate of 1.33%. The capital city, Washington, D.C. (District of Columbia), had a population of 4,098,000 in that year. Other major metropolitan areas and their estimated populations include: New York, 18,498,000; Los Angeles, 12,146,000; Chicago, 8,711,000; Dallas, 4,612,000; Houston, 4,283,000; Philadelphia, 5,325,000; San Diego, 2,818,000; and Phoenix, 3,393,000. Major cities can be found throughout the United States.


The majority of the population of the United States is of European origin, with the largest groups having primary ancestry traceable to the United Kingdom, Germany, and Ireland; many Americans report multiple ancestries. According to 2004 American Community Survey estimates, about 75.6% of the total population are white, 12.1% are blacks and African Americans, and 4.2% are Asian. Native Americans (including Alaskan Natives) account for about 0.8% of the total population. About 1.8% of the population claim a mixed ancestry of two or more races. About 11.9% of all US citizens are foreign-born, with the largest numbers of people coming from Latin America (17,973,287) and Asia (9,254,705).

Some Native American societies survived the initial warfare with land-hungry white settlers and retained their tribal cultures. Their survival, however, has been on the fringes of North American society, especially as a result of the implementation of a national policy of resettling Native American tribes on reservations. In 2004, estimates place the number of Native Americans (including Alaska Natives) at 2,151,322. The number of those who claim mixed Native American and white racial backgrounds is estimated at 1,370,675; the 2004 estimate for mixed Native American and African American ancestry was 204,832. The largest single tribal grouping is the Cherokee, with about 331,491 people. The Navajo account for about 230,401 people, the Chippewa fro 92,041 people, and the Sioux for 67,666 people. Groups of Native Americans are found most numerously in the southwestern states of Oklahoma, Arizona, New Mexico, and California. The 1960s and 1970s saw successful court fights by Native Americans in Alaska, Maine, South Dakota, and other states to regain tribal lands or to receive cash settlements for lands taken from them in violation of treaties during the 1800s.

The black and African American population in 2004 was estimated at 34,772,381, with the majority still residing in the South, the region that absorbed most of the slaves brought from Africa in the 18th and 19th centuries. About 1,141,232 people claimed mixed black and white ethnicity. Two important regional migrations of blacks have taken place: (1) a "Great Migration" to the North, commencing in 1915, and (2) a small but then unprecedented westward movement beginning about 1940. Both migrations were fostered by wartime demands for labor and by postwar job opportunities in northern and western urban centers. More than three out of four black Americans live in metropolitan areas, notably in Washington, D.C., Atlanta, Chicago, Detroit, New Orleans, Newark, Baltimore, and New York City, which had the largest number of black residents. Large-scale federal programs to ensure equality for African Americans in voting rights, public education, employment, and housing were initiated after the historic 1954 Supreme Court ruling that barred racial segregation in public schools. By 1966, however, in the midst of growing and increasingly violent expressions of dissatisfaction by black residents of northern cities and southern rural areas, the federal Civil Rights Commission reported that integration programs were lagging. Throughout the 1960s, 1970s, and 1980s, the unemployment rate among nonwhites in the United States was at least double that for whites, and school integration proceeded slowly, especially outside the South.

Also included in the US population are a substantial number of persons whose lineage can be traced to Asian and Pacific nationalities, chiefly Chinese, Filipino, Japanese, Indian, Korean, and Vietnamese. The Chinese population is highly urbanized and concentrated particularly in cities of over 100,000 population, mostly on the West Coast and in New York City. According to 2004 estimates, there are over 2.8 million Chinese in the United States. Asian Indians are the next largest group of Asians with over 2.2 million people in 2004. About 2.1 million people are Filipino. The Japanese population has risen steadily from a level of 72,157 in 1910 to about 832,039 in 2004. Hawaii has been the most popular magnet of Japanese emigration. Most Japanese in California were farmers until the outbreak of World War II, when they were interned and deprived of their landholdings; after the war, most entered the professions and other urban occupations.

Hispanics or Latinos make up about 14% of the population according to 2004 estimates. It is important to note, however, that the designation of Hispanic or Latino applies to those who are of Latin American descent; these individuals may also belong to white, Asian, or black racial groups. Although Mexicans in the 21st century were still concentrated in the Southwest, they have settled throughout the United States; there are over 25 million Mexicans in the country. Spanish-speaking Puerto Ricans, who often represent an amalgam of racial strains, have largely settled in the New York metropolitan area, where they partake in considerable measure of the hardships and problems experienced by other immigrant groups in the process of settling in the United States; there are about 3.8 million Puerto Ricans in the country. Since 1959, many Cubans have settled in Florida and other eastern states. As of 2004, there are about 1.4 mullion Cubans in the Untied States.


The primary language of the United States is English, enriched by words borrowed from the languages of Indians and immigrants, predominantly European. Very early English borrowed from neighboring French speakers such words as shivaree, butte, levee, and prairie; from German, sauerkraut, smearcase, and cranberry; from Dutch, stoop, spook, and cookie; and from Spanish, tornado, corral, ranch, and canyon. From various West African languages, blacks have given English jazz, voodoo, and okra. According to 2004 estimates of primary languages spoken at home, about 81% of the population speak English only.

When European settlement began, Indians living north of Mexico spoke about 300 different languages now held to belong to 58 different language families. Only 2 such families have contributed noticeably to the American vocabulary: Algonkian in the Northeast and Aztec-Tanoan in the Southwest. From Algonkian languages, directly or sometimes through Canadian French, English has taken such words as moose, skunk, caribou, opossum, wood-chuck, and raccoon for New World animals; hickory, squash, and tamarack for New World flora; and succotash, hominy, mackinaw, moccasin, tomahawk, toboggan, and totem for various cultural items. From Nahuatl, the language of the Aztecs, terms such as tomato, mesquite, coyote, chili, tamale, chocolate, and ocelot have entered English, largely by way of Spanish. A bare handful of words come from other Indian language groups, such as tepee from Dakota Siouan, catalpa from Creek, sequoia from Cherokee, hogan from Navaho, and sockeye from Salish, as well as cayuse from Chinook.

Professional dialect research, initiated in Germany in 1878 and in France in 1902, did not begin in the United States until 1931, in connection with the Linguistic Atlas of New England (193943). This kind of research, requiring trained field-workers to interview representative informants in their homes, subsequently was extended to the entire Atlantic Coast, the north-central states, the upper Midwest, the Pacific Coast, the Gulf states, and Oklahoma. The New England atlas, the Linguistic Atlas of the Upper Midwest (197376), and the first two fascicles of the Linguistic Atlas of the Middle and South Atlantic States (1980) have been published, along with three volumes based on Atlantic Coast field materials. Also published or nearing publication are atlases of the north-central states, the Gulf states, and Oklahoma. In other areas, individual dialect researchers have produced more specialized studies. The definitive work on dialect speech, the American Dialect Society's monumental Dictionary of American Regional English, began publication in 1985.

Dialect studies confirm that standard English is not uniform throughout the country. Major regional variations reflect patterns of colonial settlement, dialect features from England having dominated particular areas along the Atlantic Coast and then spread westward along the three main migration routes through the Appalachian system. Dialectologists recognize three main dialectsNorthern, Midland, and Southerneach with subdivisions related to the effect of mountain ranges and rivers and railroads on population movement.

The Northern dialect is that of New England and its derivative settlements in New York; the northern parts of Ohio, Indiana, Illinois, and Iowa; and Michigan, Wisconsin, northeastern South Dakota, and North Dakota. A major subdivision is that of New England east of the Connecticut River, an area noted typically by the loss of /r/ after a vowel, and by the pronunciation of can't, dance, half, and bath with a vowel more like that in father than that in fat. Generally, however, Northern speech has a strong /r/ after a vowel, the same vowel in can't and cat, a conspicuous contrast between cot and caught, the /s/ sound in greasy, creek rhyming with pick, and with ending with the same consonant sound as at the end of breath.

Midland speech extends in a wide band across the United States: there are two main subdivisions, North Midland and South Midland. North Midland speech extends westward from New Jersey, Delaware, and Pennsylvania into Ohio, Illinois, southern Iowa, and northern Missouri. Its speakers generally end with with the consonant sound that begins the word thin, pronounce cot and caught alike, and say cow and down as /caow/ and /daown/. South Midland speech was carried by the Scotch-Irish from Pennsylvania down the Shenandoah Valley into the southern Appalachians, where it acquired many Southern speech features before it spread westward into Kentucky, Tennessee, southern Missouri, Arkansas, and northeast Texas. Its speakers are likely to say plum peach rather than clingstone peach and snake doctor rather than dragonfly.

Southern speech typically, though not always, lacks the consonant /r/ after a vowel, lengthens the first part of the diphthong in write so that to Northern ears it sounds almost like rat, and diphthongizes the vowels in bed and hit so that they sound like /beuhd/ and /hiuht/. Horse and hoarse do not sound alike, and creek rhymes with meek. Corn bread is corn pone, and you-all is standard for the plural.

In the western part of the United States, migration routes so crossed and intermingled that no neat dialect boundaries can be drawn, although there are a few rather clear population pockets.

Spanish is spoken by a sizable minority in the United States; according to 2004 estimates, about 11.4% of the population speak Spanish as the primary language of their household. The majority of Spanish speakers live in the Southwest, Florida, and eastern urban centers. Refugee immigration since the 1950s has greatly increased the number of foreign-language speakers from Latin America and Asia.

Educational problems raised by the presence of large blocs of non-English speakers led to the passage in 1976 of the Bilingual Educational Act, enabling children to study basic courses in their first language while they learn English. A related school problem is that of black English, a Southern dialect variant that is the vernacular of many black students now in northern schools.


US religious traditions are predominantly Judeo-Christian and most Americans identify themselves as Protestants (of various denominations), Roman Catholics, or Jews. As of 2000, over 141 million Americans reported affiliation with a religious group. The single largest Christian denomination is the Roman Catholic Church, with membership in 2004 estimated at 66.4 million. Immigration from Ireland, Italy, Eastern Europe, French Canada, and the Caribbean accounts for the predominance of Roman Catholicism in the Northeast, Northwest, and some parts of the Great Lakes region, while Hispanic traditions and more recent immigration from Mexico and other Latin American countries account for the historical importance of Roman Catholicism in California and throughout most of the sunbelt. More than any other US religious body, the Roman Catholic Church maintains an extensive network of parochial schools.

Jewish immigrants settled first in the Northeast, where the largest Jewish population remains; at last estimates, about 6.1 million Jews live in the United States. According to data from 1995, there are about 3.7 million Muslims in the country. About 1.8 million people are Buddhist and 795,000 are Hindu. Approximately 874,000 people are proclaimed atheists.

Over 94 million persons in the United States report affiliation with a Protestant denomination. Baptists predominate below the Mason-Dixon line and west to Texas. By far the nation's largest Protestant group is the Southern Baptist Convention, which has about 16.2 million members; the American Baptist Churches in the USA claim some 1.4 million members. A concentration of Methodist groups extends westward in a band from Delaware to eastern Colorado; the largest of these groups, the United Methodist Church has about 8.2 million members. A related group, the African Methodist Episcopal Church, has about 2.5 million members. Lutheran denominations, reflecting in part the patterns of German and Scandinavian settlement, are most highly concentrated in the north-central states, especially Minnesota and the Dakotas. Two Lutheran synods, the Lutheran Church in America and the American Lutheran Church, merged in 1987 to form the Evangelical Lutheran Church in America, with more than 5 million adherents in 2004. In June 1983, the two major Presbyterian churches, the northern-based United Presbyterian Church in the USA and the southern-based Presbyterian Church in the United States, formally merged as the Presbyterian Church (USA), ending a division that began with the Civil War. This group claimed 3.4 adherents in 2004. Other prominent Protestant denominations and their estimated adherents (2004) include the Episcopal Church 2,334,000, and the United Church of Christ 1,331,000.

A number of Orthodox Christian denominations are represented in the United States, established by immigrants hoping to maintain their language and culture in a new world. The largest group of Orthodox belong to the Greek Orthodox Archdiocese of America, which has about 1.5 million members.

A number of religious groups, which now have a worldwide presence, originated in the United States. One such group, the Church of Jesus Christ of Latter-Day Saints (Mormons), was organized in New York in 1830 by Joseph Smith, Jr., who claimed to receive a revelation concerning an ancient American prophet named Mormon. The group migrated westward, in part to escape persecution, and has played a leading role in the political, economic, and religious life of Utah; Salt Lake City is the headquarters for the church. As of 2004, there are about 5.4 million members of the, the Church of Jesus Christ of Latter-Day Saints. The Jehovah's Witnesses were established by Charles Taze Russell in Pittsburgh, Pennsylvania, in 1872. They believe that Biblical prophecies are being fulfilled through world events and that the kingdom of God will be established on earth at the end of the great war described in the Bible. In 2004, there were about 1 million members in the Untied States.

The Church of Christ Scientist was established by Mary Baker Eddy (18211910) and her book Science and Health with Key to the Scriptures. A primary belief of the group is that physical injury and illness might be healed through the power of prayer and the correction of false beliefs. The Mother Church is located in Boston, Massachusetts. Christian Scientists have over 1,000 congregations in the nation. The Seventh-Day Adventists were also established in the Untied States by William Miller, a preacher who believed that the second coming of Christ would occur between 1843 and 1844. Though his prediction did not come true, many of his followers continued to embrace other practices such as worship on Saturday, vegetarianism, and a focus on preparation for the second coming. In 2004, the Seventh-Day Adventist Church had 919,000 members in the United States.


Railroads have lost not only the largest share of intercity freight traffic, their chief source of revenue, but passenger traffic as well. Despite an attempt to revive passenger transport through the development of a national network (Amtrak) in the 1970s, the rail sector has continued to experience heavy losses and declining revenues. In 1998 there were nine Class I rail companies in the United States, down from 13 in 1994, with a total of 178,222 employees and operating revenues of $32.2 billion. In 2003 there were 227,736 km (141,424 mi) of railway, all standard gauge. In 2000, Amtrak carried 84.1 million passengers.

The most conspicuous form of transportation is the automobile, and the extent and quality of the United States road-transport system are without parallel in the world. Over 226.06 million vehiclesa record numberwere registered in 2003, including more than 130.8 million passenger cars and over 95.3. commercial vehicles. In 2000, there were some 4,346,068 motorcycles registered.

The United States has a vast network of public roads, whose total length as of 2003 was 6,393,603 km (3,976,821 mi), of which, 4,180,053 km (2,599,993 mi) were paved, including 74,406 km (46,281 mi) of expressways. The United States also has 41,009 km (25,483 mi) of navigable inland channels, exclusive of the Great Lakes. Of that total, 19,312 km (12,012 mi) are still in commercial use, as of 2004.

Major ocean ports or port areas are New York, the Delaware River areas (Philadelphia), the Chesapeake Bay area (Baltimore, Norfolk, Newport News), New Orleans, Houston, and the San Francisco Bay area. The inland port of Duluth on Lake Superior handles more freight than all but the top-ranking ocean ports. The importance of this port, along with those of Chicago and Detroit, was enhanced with the opening in 1959 of the St. Lawrence Seaway. Waterborne freight consists primarily of bulk commodities such as petroleum and its products, coal and coke, iron ore and steel, sand, gravel and stone, grains, and lumber. The US merchant marine industry has been decreasing gradually since the 1950s. In 2005, the United States had a merchant shipping fleet of 486 vessels of 1,000 GRT or more, with a combined GRT of 12,436,658.

In 2004, the United States had an estimated 14,857 airports. In 2005 a total of 5,120 had paved runways, and there were also 153 heliports. Principal airports include Hartsfield at Atlanta; Logan International at Boston; O'Hare International at Chicago; Dallas-Fort Worth at Dallas; Detroit Metropolitan; Honolulu International; Houston Intercontinental; Los Angeles International; John F. Kennedy, La Guardia, and Newark International at or near New York; Philadelphia International; Orlando International; Miami International; San Francisco International; L. Munoz Marin at San Juan, Seattle-Tacoma at Seattle, and Dulles International at Wash-ington. Revenue passengers carried by the airlines in 1940 totaled 2.7 million. By 2003, the figure was estimated at 588.997 million for US domestic and international carriers, along with freight traffic estimated at 34,206 million freight ton-km.


The first Americansdistant ancestors of the Native Americansprobably crossed the Bering Strait from Asia at least 12,000 years ago. By the time Christopher Columbus came to the New World in 1492 there were probably no more than 2 million Native Americans living in the land that was to become the United States.

Following exploration of the American coasts by English, Portuguese, Spanish, Dutch, and French sea captains from the late 15th century onward, European settlements sprang up in the latter part of the 16th century. The Spanish established the first permanent settlement at St. Augustine in the future state of Florida in 1565, and another in New Mexico in 1599. During the early 17th century, the English founded Jamestown in Virginia Colony (1607) and Plymouth Colony in present-day Massachusetts (1620). The Dutch established settlements at Ft. Orange (now Albany, N.Y.) in 1624, New Amsterdam (now New York City) in 1626, and at Bergen (now part of Jersey City, N.J.) in 1660; they conquered New Swedenthe Swedish colony in Delaware and New Jerseyin 1655. Nine years later, however, the English seized this New Netherland Colony and subsequently monopolized settlement of the East Coast except for Florida, where Spanish rule prevailed until 1821. In the Southwest, California, Arizona, New Mexico, and Texas also were part of the Spanish empire until the 19th century. Meanwhile, in the Great Lakes area south of present-day Canada, France set up a few trading posts and settlements but never established effective control; New Orleans was one of the few areas of the United States where France pursued an active colonial policy.

From the founding of Jamestown to the outbreak of the American Revolution more than 150 years later, the British government administered its American colonies within the context of mercantilism: the colonies existed primarily for the economic benefit of the empire. Great Britain valued its American colonies especially for their tobacco, lumber, indigo, rice, furs, fish, grain, and naval stores, relying particularly in the southern colonies on black slave labor.

The colonies enjoyed a large measure of internal self-government until the end of the French and Indian War (174563), which resulted in the loss of French Canada to the British. To prevent further troubles with the Indians, the British government in 1763 prohibited the American colonists from settling beyond the Appalachian Mountains. Heavy debts forced London to decree that the colonists should assume the costs of their own defense, and the British government enacted a series of revenue measures to provide funds for that purpose. But soon, the colonists began to insist that they could be taxed only with their consent and the struggle grew to become one of local versus imperial authority.

Widening cultural and intellectual differences also served to divide the colonies and the mother country. Life on the edge of the civilized world had brought about changes in the colonists' attitudes and outlook, emphasizing their remoteness from English life. In view of the long tradition of virtual self-government in the colonies, strict enforcement of imperial regulations and British efforts to curtail the power of colonial legislatures presaged inevitable conflict between the colonies and the mother country. When citizens of Massachusetts, protesting the tax on tea, dumped a shipload of tea belonging to the East India Company into Boston harbor in 1773, the British felt compelled to act in defense of their authority as well as in defense of private property. Punitive measuresreferred to as the Intolerable Acts by the colonistsstruck at the foundations of self-government.

In response, the First Continental Congress, composed of delegates from 12 of the 13 coloniesGeorgia was not representedmet in Philadelphia in September 1774, and proposed a general boycott of English goods, together with the organizing of a militia. British troops marched to Concord, Mass., on 19 April 1775 and destroyed the supplies that the colonists had assembled there. American "minutemen" assembled on the nearby Lexington green and fired "the shot heard round the world," although no one knows who actually fired the first shot that morning. The British soldiers withdrew and fought their way back to Boston.

Voices in favor of conciliation were raised in the Second Continental Congress that assembled in Philadelphia on 10 May 1775, this time including Georgia; but with news of the Restraining Act (30 March 1775), which denied the colonies the right to trade with countries outside the British Empire, all hopes for peace vanished. George Washington was appointed commander in chief of the new American army, and on 4 July 1776, the 13 American colonies adopted the Declaration of Independence, justifying the right of revolution by the theory of natural rights.

British and American forces met in their first organized encounter near Boston on 17 June 1775. Numerous battles up and down the coast followed. The British seized and held the principal cities but were unable to inflict a decisive defeat on Washington's troops. The entry of France into the war on the American side eventually tipped the balance. On 19 October 1781, the British commander, Cornwallis, cut off from reinforcements by the French fleet on one side and besieged by French and American forces on the other, surrendered his army at Yorktown, Va. American independence was acknowledged by the British in a treaty of peace signed in Paris on 3 September 1783.

The first constitution uniting the 13 original statesthe Articles of Confederationreflected all the suspicions that Americans entertained about a strong central government. Congress was denied power to raise taxes or regulate commerce, and many of the powers it was authorized to exercise required the approval of a minimum of nine states. Dissatisfaction with the Articles of Confederation was aggravated by the hardships of a postwar depression, and in 1787the same year that Congress passed the Northwest Ordinance, providing for the organization of new territories and states on the frontiera convention assembled in Philadelphia to revise the articles. The convention adopted an altogether new constitution, the present Constitution of the United States, which greatly increased the powers of the central government at the expense of the states. This document was ratified by the states with the understanding that it would be amended to include a bill of rights guaranteeing certain fundamental freedoms. These freedomsincluding the rights of free speech, press, and assembly, freedom from unreasonable search and seizure, and the right to a speedy and public trial by an impartial juryare assured by the first 10 amendments to the constitution, adopted on 5 December 1791; the constitution did however recognize slavery, and did not provide for universal suffrage. On 30 April 1789 George Washington was inaugurated as the first president of the United States.

During Washington's administration, the credit of the new nation was bolstered by acts providing for a revenue tariff and an excise tax; opposition to the excise on whiskey sparked the Whiskey Rebellion, suppressed on Washington's orders in 1794. Alexander Hamilton's proposals for funding the domestic and foreign debt and permitting the national government to assume the debts of the states were also implemented. Hamilton, the secretary of the treasury, also created the first national bank, and was the founder of the Federalist Party. Opposition to the bank as well as to the rest of the Hamiltonian program, which tended to favor northeastern commercial and business interests, led to the formation of an anti-Federalist party, the Democratic-Republicans, led by Thomas Jefferson.

The Federalist Party, to which Washington belonged, regarded the French Revolution as a threat to security and property; the Democratic-Republicans, while condemning the violence of the revolutionists, hailed the overthrow of the French monarchy as a blow to tyranny. The split of the nation's leadership into rival camps was the first manifestation of the two-party system, which has since been the dominant characteristic of the US political scene (Jefferson's party should not be confused with the modern Republican Party, formed in 1854.)

The 1800 election brought the defeat of Federalist President John Adams, Washington's successor, by Jefferson; a key factor in Adam's loss was the unpopularity of the Alien and Sedition Acts (1798), Federalist-sponsored measures that had abridged certain freedoms guaranteed in the Bill of Rights. In 1803, Jefferson achieved the purchase from France of the Louisiana Territory, including all the present territory of the United States west of the Mississippi drained by that river and its tributaries; exploration and mapping of the new territory, notably through the expeditions of Meriwether Lewis and William Clark, began almost immediately. Under Chief Justice John Marshall, the US Supreme Court, in the landmark case of Marbury v. Madison, established the principle of federal supremacy in conflicts with the states and enunciated the doctrine of judicial review.

During Jefferson's second term in office, the United States became involved in a protracted struggle between Britain and Napoleonic France. Seizures of US ships and the impressment of US seamen by the British navy led the administration to pass the Embargo Act of 1807, under which no US ships were to put out to sea. After the act was repealed in 1809, ship seizures and impressment of seamen by the British continued, and were the ostensible reasons for the declaration of war on Britain in 1812 during the administration of James Madison. An underlying cause of the War of 1812, however, was land-hungry Westerners' coveting of southern Canada as potential US territory.

The war was largely a standoff. A few surprising US naval victories countered British successes on land. The Treaty of Ghent (24 December 1814), which ended the war, made no mention of impressment and provided for no territorial changes. The occasion for further maritime conflict with Britain, however, disappeared with the defeat of Napoleon in 1815.

Now the nation became occupied primarily with domestic problems and westward expansion. Because the United States had been cut off from its normal sources of manufactured goods in Great Britain during the war, textiles and other industries developed and prospered in New England. To protect these infant industries, Congress adopted a high-tariff policy in 1816.

Three events of the late 1810s and the 1820s were of considerable importance for the future of the country. The federal government in 1817 began a policy of forcibly resettling the Indians, already decimated by war and disease, in what later became known as Indian Territory (now Oklahoma); those Indians not forced to move were restricted to reservations. The Missouri Compromise (1820) was an attempt to find a nationally acceptable solution to the volatile dispute over the extension of black slavery to new territories. It provided for admission of Missouri into the Union as a slave state but banned slavery in territories to the west that lay north of 36°30. As a result of the establishment of independent Latin American republics and threats by France and Spain to reestablish colonial rule, President James Monroe in 1823 asserted that the Western Hemisphere was closed to further colonization by European powers. The Monroe Doctrine declared that any effort by such powers to recover territories whose independence the United States had recognized would be regarded as an unfriendly act.

From the 1820s to the outbreak of the Civil War, the growth of manufacturing continued, mainly in the North, and was accelerated by inventions and technological advances. Farming expanded with westward migration. The South discovered that its future lay in the cultivation of cotton. The cotton gin, invented by Eli Whitney in 1793, greatly simplified the problems of production; the growth of the textile industry in New England and Great Britain assured a firm market for cotton. Hence, during the first half of the 19th century, the South remained a fundamentally agrarian society based increasingly on a one-crop economy. Large numbers of field hands were required for cotton cultivation, and black slavery became solidly entrenched in the southern economy.

The construction of roads and canals paralleled the country's growth and economic expansion. The successful completion of the Erie Canal (1825), linking the Great Lakes with the Atlantic, ushered in a canal-building boom. Railroad building began in earnest in the 1830s, and by 1840, about 3,300 mi (5,300 km) of track had been laid. The development of the telegraph a few years later gave the nation the beginnings of a modern telecommunications network. As a result of the establishment of the factory system, a laboring class appeared in the North by the 1830s, bringing with it the earliest unionization efforts.

Western states admitted into the Union following the War of 1812 provided for free white male suffrage without property qualifications and helped spark a democratic revolution. As eastern states began to broaden the franchise, mass appeal became an important requisite for political candidates. The election to the presidency in 1928 of Andrew Jackson, a military hero and Indian fighter from Tennessee, was no doubt a result of this widening of the democratic process. By this time, the United States consisted of 24 states and had a population of nearly 13 million.

The relentless westward thrust of the United States population ultimately involved the United States in foreign conflict. In 1836, US settlers in Texas revolted against Mexican rule and established an independent republic. Texas was admitted to the Union as a state in 1845, and relations between Mexico and the United States steadily worsened. A dispute arose over the southern boundary of Texas, and a Mexican attack on a US patrol in May 1846 gave President James K. Polk a pretext to declare war. After a rapid advance, US forces captured Mexico City, and on 2 February 1848, Mexico formally gave up the unequal fight by signing the Treaty of Guadalupe Hidalgo, providing for the cession of California and the territory of New Mexico to the United States. With the Gadsden Purchase of 1853, the United States acquired from Mexico for $10 million large strips of land forming the balance of southern Arizona and New Mexico. A dispute with Britain over the Oregon Territory was settled in 1846 by a treaty that established the 49th parallel as the boundary with Canada. Thenceforth the United States was to be a Pacific as well as an Atlantic power.

Westward expansion exacerbated the issue of slavery in the territories. By 1840, abolition of slavery constituted a fundamental aspect of a movement for moral reform, which also encompassed women's rights, universal education, alleviation of working class hardships, and temperance. In 1849, a year after the discovery of gold had precipitated a rush of new settlers to California, that territory (whose constitution prohibited slavery) demanded admission to the Union. A compromise engineered in Congress by Senator Henry Clay in 1850 provided for California's admission as a free state in return for various concessions to the South. But enmities dividing North and South could not be silenced. The issue of slavery in the territories came to a head with the Kansas-Nebraska Act of 1854, which repealed the Missouri Compromise and left the question of slavery in those territories to be decided by the settlers themselves. The ensuing conflicts in Kansas between northern and southern settlers earned the territory the name "bleeding Kansas."

In 1860, the Democratic Party, split along northern and southern lines, offered two presidential candidates. The new Republican Party, organized in 1854 and opposed to the expansion of slavery, nominated Abraham Lincoln. Owing to the defection in Democratic ranks, Lincoln was able to carry the election in the electoral college, although he did not obtain a majority of the popular vote. To ardent supporters of slavery, Lincoln's election provided a reason for immediate secession. Between December 1860 and February 1861, the seven states of the Deep SouthSouth Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texaswithdrew from the Union and formed a separate government, known as the Confederate States of America, under the presidency of Jefferson Davis. The secessionists soon began to confiscate federal property in the South. On 12 April 1861, the Confederates opened fire on Ft. Sumter in the harbor of Charleston, S.C., and thus precipitated the US Civil War. Following the outbreak of hostilities, Arkansas, North Carolina, Virginia, and Tennessee joined the Confederacy.

For the next four years, war raged between the Confederate and Union forces, largely in southern territories. An estimated 360,000 men in the Union forces died of various causes, including 110,000 killed in battle. Confederate dead were estimated at 250,000, including 94,000 killed in battle. The North, with great superiority in manpower and resources, finally prevailed. A Confederate invasion of the North was repulsed at the battle of Gettysburg, Pennsylvania, in July 1863; a Union army took Atlanta in September 1864; and Confederate forces evacuated Richmond, the Confederate capital, in early April 1865. With much of the South in Union hands, Confederate Gen. Robert E. Lee surrendered to Gen. Ulysses S. Grant at Appomattox Courthouse in Virginia on 9 April.

The outcome of the war brought great changes in US life. Lincoln's Emancipation Proclamation of 1863 was the initial step in freeing some 4 million black slaves; their liberation was completed soon after the war's end by amendments to the Constitution. Lincoln's plan for the reconstruction of the rebellious states was compassionate, but only five days after Lee's surrender, Lincoln was assassinated by John Wilkes Booth as part of a conspiracy in which US Secretary of State William H. Seward was seriously wounded.

During the Reconstruction era (186577), the defeated South was governed by Union Army commanders, and the resultant bitterness of southerners toward northern Republican rule, which enfranchised blacks, persisted for years afterward. Vice President Andrew Johnson, who succeeded Lincoln as president, tried to carry out Lincoln's conciliatory policies but was opposed by radical Republican leaders in Congress who demanded harsher treatment of the South. On the pretext that he had failed to carry out an act of Congress, the House of Representatives voted to impeach Johnson in 1868, but the Senate failed by one vote to convict him and remove him from office. It was during Johnson's presidency that Secretary of State Seward negotiated the purchase of Alaska (which attained statehood in 1959) from Russia for $7.2 million.

The efforts of southern whites to regain political control of their states led to the formation of terrorist organizations like the Ku Klux Klan, which employed violence to prevent blacks from voting. By the end of the Reconstruction era, whites had reestablished their political domination over blacks in the southern states and had begun to enforce patterns of segregation in education and social organization that were to last for nearly a century.

In many southern states, the decades following the Civil War were ones of economic devastation, in which rural whites as well as blacks were reduced to sharecropper status. Outside the South, however, a great period of economic expansion began. Transcontinental railroads were constructed, corporate enterprise spurted ahead, and the remaining western frontier lands were rapidly occupied and settled. The age of big business tycoons dawned. As heavy manufacturing developed, Pittsburgh, Chicago, and New York emerged as the nation's great industrial centers. The Knights of Labor, founded in 1869, engaged in numerous strikes, and violent conflicts between strikers and strikebreakers were common. The American Federation of Labor, founded in 1886, established a nationwide system of craft unionism that remained dominant for many decades. During this period, too, the woman's rights movement organized actively to