section_path: Abstract
section_name: Abstract
paragraph_text: 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 a federal capital district, Washington, D.C. The 48 contiguous states border Canada to the north and Mexico to the south, with the semi-exclave of Alaska in the northwest and the archipelago of Hawaii in the Pacific Ocean. The United States also asserts sovereignty over five major island territories and various uninhabited islands in Oceania and the Caribbean. It is a megadiverse country, with the world's third-largest land area and third-largest population, exceeding 340 million. 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 from North Asia to North America over 12,000 years ago, and formed various civilizations. Spanish colonization led to the establishment in 1513 of Spanish Florida, the first European colony in what is now the continental United States. British colonization began with the first settlement of the Thirteen Colonies in Virginia in 1607. Forced migration of enslaved Africans provided the labor force necessary to make the plantation economy of the Southern Colonies economically viable. Clashes with the British Crown over taxation and the denial of parliamentary representation sparked the American Revolution, with the Second Continental Congress formally declaring independence on July 4, 1776. Victory in the 1775–1783 Revolutionary War brought international recognition of U.S. sovereignty, and the country continued to expand westward across North America, resulting in the dispossession of native inhabitants. 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, the newly passed Thirteenth Amendment freed many slaves. By 1900, the country had established itself as a great power, a status solidified after its involvement in World War I. Following 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 and led to the Cold War, during which 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.
  
  The U.S. national government is a presidential constitutional federal republic and representative 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. In addition, 574 Native tribes have sovereignty rights, with 326 reservations composing Indian country. 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 developed country, the U.S. ranks high in economic competitiveness, productivity, innovation, and higher education. The U.S. 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 the most wealth of any country and has the highest disposable household income per capita among OECD countries, though U.S. wealth inequality is one of the most pronounced in those countries. A melting pot of many ethnicities and customs, the culture of the U.S. has been shaped by centuries of immigration, and its soft power influence has a global reach. The U.S. is a member of multiple international organizations and plays a leading role in global political, cultural, economic, and military affairs.