United States

The United States of America (USA), commonly known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and the federal capital district of Washington, D.C. The 48 contiguous states border Canada to the north and Mexico to the south, with the semi-exclavic state of Alaska in the northwest and the archipelagic state of Hawaii in the Pacific Ocean. Indian country includes 574 federally recognized tribes and 326 Indian reservations with tribal sovereignty rights. The U.S. asserts sovereignty over five major island territories and various uninhabited islands.[l] It is a megadiverse country, with the world's third-largest land area[e] and third-largest population, exceeding 340 million.[m] Its three largest metropolitan areas are New York, Los Angeles, and Chicago, and its three most populous states are California, Texas, and Florida.

Paleo-Indians migrated to North America across the Bering land bridge more than 12,000 years ago, and formed civilizations and societies. Spanish exploration and colonization led to the establishment of Spanish Florida in 1513, the first European colony in what is now the continental United States. French colonization began in 1562, but permanent settlements came later. Subsequent British colonization led to the first settlement of the Thirteen Colonies in Virginia in 1607. Intensive agriculture in the rapidly expanding Southern Colonies encouraged the forced migration of enslaved Africans. Clashes with the British Crown over taxation and political representation sparked the American Revolution, with the Second Continental Congress formally declaring independence on July 4, 1776.

The United States emerged victorious from the 1775–1783 Revolutionary War and expanded westward across North America, dispossessing Native Americans during the Indian Wars. Expansion began when the U.S. signed the 1803 Louisiana Purchase with Napoleonic France. The end of the Mexican–American War saw the acquisition of further territory. As more states were admitted, a North–South division over slavery led to the secession of the Confederate States of America, which fought the Union in the 1861–1865 American Civil War. With the victory and preservation of the United States, slavery was abolished nationally. In the late 19th century the United States established itself as a great power with victory in the Spanish-American War, a status solidified after its involvement in World War I. After Japan's attack on Pearl Harbor in December 1941, the U.S. entered World War II; its aftermath left the U.S. and the Soviet Union as the world's superpowers. During the Cold War, both countries struggled for ideological dominance and international influence. The Soviet Union's collapse and the end of the Cold War in 1991 left the U.S. as the world's sole superpower, with significant geopolitical influence globally.

The U.S. national government is a constitutional presidential republic and liberal democracy with three separate branches: legislative, executive, and judicial. It has a bicameral national legislature composed of the House of Representatives, a lower house based on population, and the Senate, an upper house based on equal representation for each state. Federalism provides substantial autonomy to the 50 states, while American values are based on a democratic political tradition that draws its inspiration from the European Enlightenment movement. Since the 1850s, the Democratic and Republican parties have dominated American politics. A melting pot of many ethnicities and customs, the culture of the United States has been shaped by centuries of immigration, and its soft power influence has a global reach.

One of the world's most developed countries, the U.S. ranks among the highest in economic competitiveness, productivity, innovation, and higher education. The United States accounted for over a quarter of nominal global economic output in 2024, and its economy has been the world's largest by nominal GDP since about 1890. It possesses by far the largest amount of wealth of any country and has the highest disposable household income per capita among OECD countries, though U.S. wealth inequality is higher than in most other developed countries. The U.S. is a member of multiple international organizations and plays a leading role in global political, cultural, economic, and military affairs.