about half the size of Russia; about three-tenths the size of Africa; about one-half the size of South America (or slightly larger than Brazil); slightly smaller than China; about two and one-half times the size of Western Europe

note:

includes only the 50 states and District of Columbia

Land boundaries:

total 12,248 km, Canada 8,893 km (including 2,477 km with Alaska), Cuba 29 km (US Naval Base at Guantanamo Bay), Mexico 3,326 km

Coastline:

19,924 km

Maritime claims:

contiguous zone:

12 nm

continental shelf:

not specified

exclusive economic zone:

200 nm

territorial sea:

12 nm

International disputes:

maritime boundary disputes with Canada (Dixon Entrance, Beaufort Sea, Strait of Juan de Fuca, Machias Seal Island); 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 Navassa Island; US has made no territorial claim in Antarctica (but has reserved the right to do so) and does not recognize the claims of any other nation; Republic of Marshall Islands claims Wake Island

Climate:

mostly temperate, but tropical in Hawaii and Florida and 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

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

Natural resources:

coal, copper, lead, molybdenum, phosphates, uranium, bauxite, gold, iron, mercury, nickel, potash, silver, tungsten, zinc, petroleum, natural gas, timber

Land use:

arable land:

20%

permanent crops:

meadows and pastures:

26%

forest and woodland:

29%

other:

25%

Irrigated land:

181,020 sq km (1989 est.)

Environment:

current issues:

air pollution resulting in acid rain in both the US and Canada; the US is the largest single emitter of carbon dioxide from the burning of fossil fuels; water pollution from runoff of pesticides and fertilizers; very limited natural fresh water resources in much of the western part of the country require careful management; desertification

natural hazards:

tsunamis, volcanoes, and earthquake activity around Pacific Basin; hurricanes along the Atlantic coast; tornadoes in the midwest; mudslides in California; forest fires in the west; flooding; permafrost in northern Alaska is a major impediment to development

international agreements:

party to - Air Pollution, Air Pollution-Nitrogen Oxides, Antarctic Treaty, Climate Change, Endangered Species, Environmental Modification, Marine Dumping, Marine Life Conservation, Nuclear Test Ban, Ozone Layer Protection, Ship Pollution, Tropical Timber 83, Wetlands, Whaling; signed, but not ratified - Air Pollution-Volatile Organic Compounds, Antarctic-Environmental Protocol, Biodiversity, Desertification, Hazardous Wastes, Tropical Timber 94

Note:

world's fourth-largest country (after Russia, Canada, and China)