Countries of the world

United States

August 31, 2012, 1:24 pm
Source: CIA World Factbook
Content Cover Image

Source: NASA

The United States of America (also USA, the United States, the U.S. and sometime simply America) is a nation of 313 million people in North America, bordering both the North Atlantic Ocean and the North Pacific Ocean, between Canada and Mexico.

By area, the United States is the third largest country in the world (after Russia and Canada); about half the size of Russia; about three-tenths the size of Africa; about half the size of South America (or slightly larger than Brazil); slightly larger than China; more than twice the size of the European Union.

The United States is also the third nmost populous country in the world (after China and India)

Its major environmental issues include:

  • Air pollution resulting in acid rain in both the USA and Canada;
  • Until 2007, the US was the largest single emitter of carbon dioxide from the burning of fossil fuels; since then China has been the largest emitter;
  • Water pollution from runoff of herbicides, pesticides and fertilizers;
  • Limited natural freshwater resources in much of the western part of the country require careful management; and,
  • Desertification

Britain's American colonies broke with the mother country in 1776 and were recognized as the new nation of the United States of America following the Treaty of Paris in 1783.

During the 19th and 20th centuries, 37 new states were added to the original 13 as the nation expanded across the North American continent and acquired a number of overseas possessions.

The two most traumatic experiences in the nation's history were the Civil War (1861-65), in which a northern Union of states defeated a secessionist Confederacy of 11 southern slave states, and the Great Depression of the 1930s, an economic downturn during which about a quarter of the labor force lost its jobs.

Buoyed by victories in World Wars I and II and the end of the Cold War in 1991, the US remains the world's most powerful nation state.

Since the end of World War II, the economy has achieved relatively steady growth, low unemployment and inflation, and rapid advances in technology.


Location: North America, bordering both the North Atlantic Ocean and the North Pacific Ocean, between Canada and Mexico

Geographic Coordinates: 38 00 N, 97 00 W

Area: 9,826,675 sq km  (land: 9,161,966 sq km; water: 664,709 sq km) Note: includes only the 50 states and District of Columbia

Land Boundaries: 12,034 km  (Canada 8,893 km which includes 2,477 km with Alaska, Mexico 3,141 km) Note: US Naval Base at Guantanamo Bay, Cuba is leased by the US and is part of Cuba; the base boundary is 28 km. Much of the boundary between the United States and Mexico is defined by the Rio Grande River

Coastline: 19,924 km

Maritime Claims:

territorial sea: 12 nm
contiguous zone: 24 nm
exclusive economic zone: 200 nm
continental shelf: not specified

Natural Hazards: tsunamis; volcanoes; earthquake activity around Pacific Basin; hurricanes along the Atlantic and Gulf of Mexico coasts; tornadoes in the Midwest and Southeast; mud slides in California; forest fires in the west; flooding; permafrost in northern Alaska, a major impediment to development

See: Earthquakes in the United States - Risk, Detection, Warning, and Research

Volcanism: the United States experiences volcanic activity in the Hawaiian Islands, Western Alaska, the Pacific Northwest, and in the Northern Mariana Islands; both Mauna Loa (elev. 4,170 m) in Hawaii and Mount Rainier (elev. 4,392 m) in Washington have been deemed "Decade Volcanoes" by the International Association of Volcanology and Chemistry of the Earth's Interior, worthy of study due to their explosive history and close proximity to human populations.

Pavlof (elev. 2,519 m) is the most active volcano in Alaska's Aleutian Arc and poses a significant threat to air travel since the area constitutes a major flight path between North America and East Asia.

St. Helens (elev. 2,549 m, famous for the devastating 1980 eruption, remains active today.

Numerous other historically active volcanoes exist, mostly concentrated in the Aleutian arc and Hawaii. They include: in Alaska: Aniakchak, Augustine, Chiginagak, Fourpeaked, Iliamna, Katmai, Kupreanof, Martin, Novarupta, Redoubt, Spurr, Wrangell; in Hawaii: Trident, Ugashik-Peulik, Ukinrek Maars, Veniaminof; in the Northern Mariana Islands: Anatahan; and in the Pacific Northwest: Mount Baker, and Mount Hood. See: Hawaii Volcanoes National Park

Terrain: vast central plain, mountains in west, hills and low mountains in east; rugged mountains and broad river valleys in Alaska; rugged, volcanic topography in Hawaii.  The highest point is  Mount McKinley (6,194 m) and the lowest point Death Valley (-86 m).Note: the peak of Mauna Kea (4,207 m above sea level) on the island of Hawaii rises about 10,200 m above the Pacific Ocean floor; by this measurement, it is the world's tallest mountain - higher than Mount Everest, which is recognized as the tallest mountain above sea level.

Togography of the 48 continguous states. Source: NOAA


Sunrise over the city of Denver with the Rocky Mountains in the background. Source: Creative Commons


Climate: mostly temperate, but tropical in Hawaii and Florida, arctic in Alaska, semiarid in the great plains west of the Mississippi River, and arid in the Great Basin of the southwest; low winter temperatures in the northwest are ameliorated occasionally in January and February by warm chinook winds from the eastern slopes of the Rocky Mountains.

Climate zones under the Köppen Climate Classification SystemSource: Murray C. Peel, University of Melborne.


Ecology and Biodiversity

Map of Ecoregions of the continental United States. Source: World Wildlife Fund.

  1. New England-Acadian forests
  2. Northeastern coastal forests
  3. Atlantic coastal pine barrens
  4. Middle Atlantic coastal forests
  5. Southeastern mixed forests
  6. Southeastern conifer forests
  7. Florida sand pine scrub
  8. Everglades
  9. South Florida rocklands
  10. Appalachian-Blue Ridge forests
  11. Appalachian mixed mesophytic forests
  12. Allegheny Highlands forests
  13. Eastern forest-boreal transition
  14. Eastern Great Lakes lowland forests
  15. Southern Great Lakes forests
  16. Central U.S. hardwood forests
  17. Mississippi lowland forests
  18. Ozark Mountain forests
  19. Piney Woods forests
  20. Western Gulf coastal grasslands
  21. Tamaulipan mezquital
  22. East Central Texas forests
  23. Texas blackland prairies
  24. Edwards Plateau savanna
  25. Central forest-grasslands transition
  26. Upper Midwest forest-savanna transition
  27. Western Great Lakes forests
  28. Central tall grasslands
  29. Flint Hills tall grasslands
  30. Central and Southern mixed grasslands
  31. Nebraska Sand Hills mixed grasslands
  32. Western short grasslands
  33. Chihuahuan Desert
  1. Sierra Madre Oriental pine-oak forests
  2. Arizona Mountains forests
  3. Colorado Plateau shrublands
  4. Colorado Rockies forests
  5. Wyoming Basin shrub steppe
  6. Northern short grasslands
  7. Montana Valley and Foothill grasslands
  9. South Central Rockies forests
  10. North Central Rockies forests
  11. Okanagan dry forests
  12. Cascade Mountains leeward forests
  13. British Columbia mainland coastal forests
  14. Puget lowland forests
  15. Central Pacific coastal forests
  16. Willamette Valley forests
  17. Central and Southern Cascades forests
  18. Eastern Cascades forests
  19. Palouse grasslands
  20. Blue Mountains forests
  21. Snake-Columbia shrub steppe
  22. Wasatch and Uinta montane forests
  23. Great Basin shrub steppe
  24. Great Basin montane forests
  25. Mojave Desert
  26. Sonoran desert
  27. Sierra Nevada forests
  28. Klamath-Siskiyou forests
  29. Northern California coastal forests
  30. California interior chaparral and woodlands
  31. California Central Valley grasslands
  32. California montane chaparral and woodlands
  33. California coastal sage and chaparral

In Alaska:

  1. Arctic coastal tundra
  2. Arctic foothills tundra
  3. Brooks-British Range tundra
  4. Interior Yukon-Alaska alpine tundra
  5. Interior Alaska-Yukon lowland taiga
  6. Ogilvie-MacKenzie alpine tundra
  7. Beringia upland tundra
  8. Beringia lowland tundra
  9. Alaska Peninsula montane taiga
  10. Aleutian Islands tundra
  11. Cook Inlet taiga
  12. Alaska-St. Elias Range tundra
  13. Pacific Coastal Mountain icefields and tundra
  14. Northern Pacific coastal forests

In Hawaii:

  1. Hawaii tropical moist forests
  2. Hawaii tropical high shrublands
  3. Hawaii tropical dry forests

See also:


A view of Georges Bank, a large elevated area of the sea floor that separates the Gulf of Maine from the Atlantic Ocean. The Bank is situated east of Cape Cod, Massachusetts (US; on the left) and southwest of Cape Sable Island, Nova Scotia (Canada; upper right). Photo courtesy of NASA.

See National Parks:

Aerial view of the Colorado River as it snakes through the majestic Grand Canyon in Arizona. The sedimentary layers exposed in the canyon date back 2 billion years.

People and Society

Population: 313,847,465 (July 2012 est.)

The Dry Tortugas are a group of islands located some 120 km (75 mi) west of Key West, Florida; they form the western end of the Florida Keys in the Gulf of Mexico. Like the Keys, the Dry Tortugas are formed primarily of coral reefs over older limestone formations. The islands were named "Dry Tortugas" upon discovery by Ponce de Leon in 1513 - "tortugas" means turtles in Spanish, and the islands are "dry" as no fresh water is found on them. Accessible only by boat or seaplane, the islands nevertheless have been designated a national park and are visited by hundreds every year. This view highlights three islands in the group: Bush Key, Hospital Key, and Garden Key - the site of hexagonal Civil War-era Fort Jefferson. Image courtesy of NASA.

Ethnic Groups: white 79.96%, black 12.85%, Asian 4.43%, Amerindian and Alaska native 0.97%, native Hawaiian and other Pacific islander 0.18%, two or more races 1.61% (July 2007 estimate) 

Note: a separate listing for Hispanic is not included because the US Census Bureau considers Hispanic to mean persons of Spanish/Hispanic/Latino origin including those of Mexican, Cuban, Puerto Rican, Dominican Republic, Spanish, and Central or South American origin living in the US who may be of any race or ethnic group (white, black, Asian, etc.); about 15.1% of the total US population is Hispanic.

Age Structure:

0-14 years: 20.1% (male 32,107,900/female 30,781,823)
15-64 years: 66.8% (male 104,411,352/female 104,808,064)
65 years and over: 13.1% (male 17,745,363/female 23,377,542) (2011 est.)

Population Growth Rate: 0.899% (2012 est.)

Birthrate: 13.68 births/1,000 population (2012 est.)

Death Rate: 8.39 deaths/1,000 population (July 2012 est.)

Net Migration Rate: 3.62 migrant(s)/1,000 population (2012 est.)

Life Expectancy at Birth: 78.49 years 

male: 76.05 years
female: 81.05 years (2012 est.)

Total Fertility Rate: 2.06 children born/woman (2012 est.)

Languages:  English 82.1%, Spanish 10.7%, other Indo-European 3.8%, Asian and Pacific island 2.7%, other 0.7% (2000 census). Note: Hawaiian is an official language in the state of Hawaii.

Literacy (age 15 and over can read and write)99% (2003 est.)

Urbanization: 82% of total population (2010) growing at an annual rate of change of 1.2% (2010-15 est.)


Government Type: Constitution-based federal republic; strong democratic tradition

Capital: Washington - 4.421 million (2009)

Other Major Cities: New York-Newark 19.3 million; Los Angeles-Long Beach-Santa Ana 12.675 million; Chicago 9.134 million; Miami 5.699 million (2009)

This false-color satellite image shows greater New York City. The Island of Manhattan is jutting southward from top center, bordered by the Hudson River to the west and the East River to the east. (North is straight up in this scene.) In the middle of Manhattan, Central Park appears as a long green rectangle running roughly north-south with a large lake in the middle. Also visible are parts of Staten Island (bottom left corner) and Long Island (lower right). Photo courtesy of NASA.


Los Angeles at night as seen from the International Space Station. After sunset, the borders of "The City of Angels" are defined as much by its dark terrain features as by its well-lit grid of streets and freeways. Over 13 million people inhabit the coastal basin bounded roughly by the Santa Monica and San Gabriel Mountains to the north and the Chino Hills and Santa Ana Mountains to the east and southeast. Image courtesy of NASA.


Administrative divisions:  50 states and 1 district*; Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia*, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming.


Dependent Areas: American Samoa, Baker Island, Guam, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Islands, Navassa Island, Northern Marianna Islands, Palmyra Atoll, Puerto Rico, United States Virgin Islands, Wake Island

Note: from 18 July 1947 until 1 October 1994, the US administered the Trust Territory of the Pacific Islands; it entered into a political relationship with all four political entities: the Northern Mariana Islands is a commonwealth in political union with the US (effective 3 November 1986); the Republic of the Marshall Islands signed a Compact of Free Association with the US (effective 21 October 1986); the Federated States of Micronesia signed a Compact of Free Association with the US (effective 3 November 1986); Palau concluded a Compact of Free Association with the US (effective 1 October 1994).

Independence Date: 4 July 1776 (declared); 3 September 1783 (recognized by Great Britain)

Legal System: common law system based on English common law at the federal level; state legal systems based on common law except Louisiana, which is based on Napoleonic civil code; judicial review of legislative acts. The United States withdrew acceptance of compulsory International Court of Justics (ICJ) jurisdiction in 2005;and withdrew acceptance of International Criminal Court (ICCt) jurisdiction in 2002.

International Environmental Agreements

The United States is party to international agreements on: Air Pollution, Air Pollution-Nitrogen Oxides, Antarctic-Environmental Protocol, Antarctic-Marine Living Resources, Antarctic Seals, Antarctic Treaty, Climate Change, Desertification, Endangered Species, Environmental Modification, Marine Dumping, Marine Life Conservation, Ozone Layer Protection, Ship Pollution, Tropical Timber 83, Tropical Timber 94, Wetlands, and Whaling.

It has signed, but not ratified international agreements on: Air Pollution-Persistent Organic Pollutants, Air Pollution-Volatile Organic Compounds, Biodiversity, Climate Change-Kyoto Protocol, and Hazardous Wastes.

See: Kyoto Protocol and the United States


Total Renewable Water Resources: 3069 cubic kilometers (1985)

Major Rivers: Mississippi River, Columbia River, Yukon River, Colorado River, Arkansas River, Snake River.

Freshwater Withdrawal: 477 cu km/yr  (13% domestic, 46% industrial, 41% agricultural)

Per Capita Freshwater Withdrawal: 1,600 cu m/yr (2000)

Completed in 1935, Hoover Dam on the Colorado River straddles the Arizona-Nevada border.


Agricultural products: wheat, corn, other grains, fruits, vegetables, cotton; beef, pork, poultry, dairy products; fish; forest products

Irrigated Land: 230,000 sq km (2008)

Gascoyne, North Dakota, part of the Great Plains that cover much of the central portion of the United States. Source: Andrew Filer


Natural Resources: coal, copper, lead, molybdenum, phosphates, rare earth elements, uranium, bauxite, gold, iron, mercury, nickel, potash, silver, tungsten, zinc, petroleum, natural gas, timber. Note: the US has the world's largest coal reserves with 491 billion short tons accounting for 27% of the world's total.

Land Use:

arable land: 18.01%
permanent crops: 0.21%
other: 81.78% (2005)


The US has the largest and most technologically powerful economy in the world, with a per capita GDP of $48,100.

In this market-oriented economy, private individuals and business firms make most of the decisions, and the federal and state governments buy needed goods and services predominantly in the private marketplace. USA business firms enjoy greater flexibility than their counterparts in Western Europe and Japan in decisions to expand capital plant, to lay off surplus workers, and to develop new products. At the same time, they face higher barriers to enter their rivals' home markets than foreign firms face entering USA markets.

USA firms are at or near the forefront in technological advances, especially in computers and in medical, aerospace, and military equipment; their advantage has narrowed since the end of World War II.

The onrush of technology largely explains the gradual development of a "two-tier labor market" in which those at the bottom lack the education and the professional/technical skills of those at the top and, more and more, fail to get comparable pay raises, health insurance coverage, and other benefits.

Since 1975, practically all the gains in household income have gone to the top 20% of households.

Since 1996, dividends and capital gains have grown faster than wages or any other category of after-tax income.

Imported oil accounts for nearly 55% of US consumption. Oil prices doubled between 2001 and 2006, the year home prices peaked; higher gasoline prices ate into consumers' budgets and many individuals fell behind in their mortgage payments. Oil prices increased another 50% between 2006 and 2008. In 2008, soaring oil prices threatened inflation and caused a deterioration in the US merchandise trade deficit, which peaked at $840 billion.

In 2009, with the global recession deepening, oil prices dropped 40% and the US trade deficit shrank, as US domestic demand declined, but in 2011 the trade deficit ramped back up to $803 billion, as oil prices climbed once more. The global economic downturn, the sub-prime mortgage crisis, investment bank failures, falling home prices, and tight credit pushed the United States into a recession by mid-2008. GDP contracted until the third quarter of 2009, making this the deepest and longest downturn since the Great Depression.

To help stabilize financial markets, in October 2008 the US Congress established a $700 billion Troubled Asset Relief Program (TARP). The government used some of these funds to purchase equity in US banks and industrial corporations, much of which had been returned to the government by early 2011. In January 2009 the US Congress passed and President Barack Obama signed a bill providing an additional $787 billion fiscal stimulus to be used over 10 years - two-thirds on additional spending and one-third on tax cuts - to create jobs and to help the economy recover.

In 2010 and 2011, the federal budget deficit reached nearly 9% of GDP; total government revenues from taxes and other sources are lower, as a percentage of GDP, than that of most other developed countries.

The wars in Iraq and Afghanistan required major shifts in national resources from civilian to military purposes and contributed to the growth of the US budget deficit and public debt - through 2011, the direct costs of the wars totaled nearly $900 billion, according to US government figures.

In March 2010, President Obama signed a health insurance reform bill into law that will extend coverage to an additional 32 million American citizens by 2016, through private health insurance for the general population and Medicaid for the impoverished.

In July 2010, the president signed the Dodd-Frank Wall Street Reform and Consumer Protection Act, a bill designed to promote financial stability by protecting consumers from financial abuses, ending taxpayer bailouts of financial firms, dealing with troubled banks that are "too big to fail," and improving accountability and transparency in the financial system - in particular, by requiring certain financial derivatives to be traded in markets that are subject to government regulation and oversight.

Long-term problems include inadequate investment in deteriorating infrastructure, rapidly rising medical and pension costs of an aging population, sizable current account and budget deficits - including significant budget shortages for state governments - energy shortages, and stagnation of wages in lower-income families.

GDP: (Purchasing Power Parity): $15.04 trillion (2011 est.)

Note: In 2011, the combined GDP of the twenty-seven Nations that form the  European Union was slightly higher at $15.39 trillion

GDP: (Official Exchange Rate): $15.06 trillion (2011 est.)

GDP- per capita (PPP): $48,100 (2011 est.)

Note that this is the 11th largest GDP per capita behind Liechtenstein, Qatar, Luxembourg, Bermuda (UK), Singapore, Jersey (UK), Falkland Islands (Islas Malvinas), Norway, Brunei, and United Arab Emirates.

GDP- composition by sector:

agriculture: 1.2%
industry: 22.1%
services: 76.7% (2011 est.)

Industries: highly diversified, world leading, high-technology innovator, second largest industrial output in world; petroleum, steel, motor vehicles, aerospace, telecommunications, chemicals, electronics, food processing, consumer goods, lumber, mining

Currency: US dollar

International Disputes:

  • the US has intensified domestic security measures and is collaborating closely with its neighbors, Canada and Mexico, to monitor and control legal and illegal personnel, transport, and commodities across the international borders;

  • abundant rainfall in recent years along much of the Mexico-US border region has ameliorated periodically strained water-sharing arrangements;

  • 1990 Maritime Boundary Agreement in the Bering Sea still awaits Russian Duma ratification;

  • Canada and the USA dispute how to divide the Beaufort Sea and the status of the Northwest Passage but continue to work cooperatively to survey the Arctic continental shelf;

  • The Bahamas and USA have not been able to agree on a maritime boundary;

  • US Naval Base at Guantanamo Bay is leased from Cuba and only mutual agreement or US abandonment of the area can terminate the lease;

  • Haiti claims US-administered Navassa Island;

  • USA has made no territorial claim in Antarctica (but has reserved the right to do so) and does not recognize the claims of any other states;

  • Marshall Islands claims Wake Island;

  • Tokelau included American Samoa's Swains Island among the islands listed in its 2006 draft constitution




Agency, C. (2012). United States. Retrieved from


To add a comment, please Log In.