US River Basin Map

The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. It consists of 50 states, a

federal district A federal district is a type of administrative division of a federation, usually under the direct control of a federal government and organized sometimes with a single municipal body. Federal districts often include capital districts, and they e ...

, five major

unincorporated territories Territories of the United States are sub-national administrative divisions overseen by the federal government of the United States. The various American territories differ from the U.S. states and tribal reservations as they are not sover ...

, nine Minor Outlying Islands, and 326

Indian reservation An Indian reservation is an area of land held and governed by a federally recognized Native American tribal nation whose government is accountable to the United States Bureau of Indian Affairs and not to the state government in which it ...

s. The United States is also in free association with three Pacific Island

sovereign states A sovereign state or sovereign country, is a political entity represented by one central government that has supreme legitimate authority over territory. International law defines sovereign states as having a permanent population, defined terri ...

: the

Federated States of Micronesia The Federated States of Micronesia (; abbreviated FSM) is an island country in Oceania. It consists of four states from west to east, Yap, Chuuk, Pohnpei and Kosraethat are spread across the western Pacific. Together, the states comprise a ...

, the

Marshall Islands The Marshall Islands ( mh, Ṃajeḷ), officially the Republic of the Marshall Islands ( mh, Aolepān Aorōkin Ṃajeḷ),'' () is an independent island country and microstate near the Equator in the Pacific Ocean, slightly west of the Internati ...

, and the Republic of Palau. It is the world's third-largest country by both land and total area. It shares land borders with Canada to its north and with Mexico to its south and has maritime borders with the

Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the Atlantic Ocean, North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to ...

Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

, and other nations. With a population of over 333 million, it is the most populous country in the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

and the third most populous in the world. The national capital of the United States is

Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...

and its most populous city and principal

financial center A financial centre ( BE), financial center ( AE), or financial hub, is a location with a concentration of participants in banking, asset management, insurance or financial markets with venues and supporting services for these activities to t ...

New York City New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...

. Paleo-Americans migrated from Siberia to the North American mainland at least 12,000 years ago, and advanced cultures began to appear later on. These societies had almost completely declined when

Europeans Europeans are the focus of European ethnology, the field of anthropology related to the various ethnic groups that reside in the states of Europe. Groups may be defined by common genetic ancestry, common language, or both. Pan and Pfeil (2004) ...

arrived in North America and began colonizing it.

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...

Thirteen Colonies The Thirteen Colonies, also known as the Thirteen British Colonies, the Thirteen American Colonies, or later as the United Colonies, were a group of Kingdom of Great Britain, British Colony, colonies on the Atlantic coast of North America. Fo ...

quarreled with the British Crown over taxation and political representation, leading to the

American Revolution The American Revolution was an ideological and political revolution that occurred in British America between 1765 and 1791. The Americans in the Thirteen Colonies formed independent states that defeated the British in the American Revolut ...

(1765–1791). After the Revolution, the United States gained independence, the first

nation-state A nation state is a political unit where the state and nation are congruent. It is a more precise concept than "country", since a country does not need to have a predominant ethnic group. A nation, in the sense of a common ethnicity, may inc ...

founded on

Enlightenment Enlightenment or enlighten may refer to: Age of Enlightenment * Age of Enlightenment, period in Western intellectual history from the late 17th to late 18th century, centered in France but also encompassing (alphabetically by country or culture): ...

principles of

liberal democracy Liberal democracy is the combination of a liberal political ideology that operates under an indirect democratic form of government. It is characterized by elections between multiple distinct political parties, a separation of powers into diff ...

. In the late 18th century, the U.S. began expanding across North America, gradually obtaining new territories, sometimes through war, frequently displacing Native Americans, and admitting new states. By 1848, the United States spanned the

continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...

from east to west. The controversy surrounding the practice of

slavery Slavery and enslavement are both the state and the condition of being a slave—someone forbidden to quit one's service for an enslaver, and who is treated by the enslaver as property. Slavery typically involves slaves being made to perf ...

culminated in the secession of the

Confederate States of America The Confederate States of America (CSA), commonly referred to as the Confederate States or the Confederacy was an unrecognized breakaway republic in the Southern United States that existed from February 8, 1861, to May 9, 1865. The Confeder ...

, which fought the remaining states of the

Union Union commonly refers to: * Trade union, an organization of workers * Union (set theory), in mathematics, a fundamental operation on sets Union may also refer to: Arts and entertainment Music * Union (band), an American rock group ** ''Un ...

during the

American Civil War The American Civil War (April 12, 1861 – May 26, 1865; also known by other names) was a civil war in the United States. It was fought between the Union ("the North") and the Confederacy ("the South"), the latter formed by states th ...

(1861–1865). With the Union's victory and preservation, slavery was abolished by the Thirteenth Amendment. By 1890, the United States had grown to become the world's largest economy, and the

Spanish–American War , partof = the Philippine Revolution, the decolonization of the Americas, and the Cuban War of Independence , image = Collage infobox for Spanish-American War.jpg , image_size = 300px , caption = (clock ...

and

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

established the country as a world power. After Japan's surprise attack on Pearl Harbor in 1941, the U.S. entered

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

on the Allied side. The aftermath of the war left the United States and the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...

as the world's two

superpower A superpower is a state with a dominant position characterized by its extensive ability to exert influence or project power on a global scale. This is done through the combined means of economic, military, technological, political and cultural s ...

s, and led to the

Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...

, which commenced in 1945 and ended in 1991 with the Soviet Union's dissolution. During the Cold War, both countries engaged in a struggle for ideological dominance but avoided direct military conflict. They also competed in the

Space Race The Space Race was a 20th-century competition between two Cold War rivals, the United States and the Soviet Union, to achieve superior spaceflight capability. It had its origins in the ballistic missile-based nuclear arms race between the tw ...

, which culminated in the 1969 American spaceflight in which the U.S. was the first nation to land humans on the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

. Simultaneously, the