United States

The United States of America (USA), also 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 Washington, D.C. as its federal capital district. 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. The U.S. also asserts federal sovereignty over five major island territories and various uninhabited islands,[k] while over 326 Indian reservations occupied by federally recognized Native American tribes are treated as "domestic dependent nations" with tribal sovereignty rights.[18] The U.S. is a megadiverse country, with the world's third-largest land area[d] and third-largest population, exceeding 340 million.[l] 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 various civilizations and societies. Spanish exploration and colonization led to the establishment in 1513 of Spanish Florida, the first European colony in what is now the continental United States. France also began to colonize at this time, but major settlements came much 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 as it fought the Indian Wars. Expansion continued when the U.S. signed the 1803 Louisiana Purchase with Napoleonic France and won the Mexican–American War in 1848. 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. By the late 19th century, the United States established itself as a great power with victory in the Spanish-American War, a status solidified with its participation in World War I. Following Japan's attack on Pearl Harbor in December 1941, the U.S. entered World War II. The aftermath of the war left the U.S. and the Soviet Union as the world's two superpowers which led to the Cold War, during which both countries struggled for ideological dominance and international influence. The end of the Cold War and the Soviet Union's collapse in 1991 left the U.S. as the world's sole superpower, with significant geopolitical influence globally.

The U.S. national government is a presidential constitutional federal 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. The country's Democratic and Republican parties have dominated American politics since the 1850s. Federalism provides substantial autonomy to the 50 states, while American values are based on a political tradition that draws its inspiration from the European Enlightenment movement. 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, human rights, 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.