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 consisting 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 341 million.
Paleo-Indians first migrated from North Asia to North America at least 15,000 years ago, and formed various civilizations. European discovery of the Americas began in 1492, and British colonization followed with the 1607 settlement of Virginia, the first of the Thirteen Colonies. The American Enlightenment that spread throughout the colonies in the 18th century valued republicanism and liberalism. Clashes with the British Crown over taxation without parliamentary representation and the denial of other English rights evolved into the American Revolution, which led to the July 2, 1776, Lee Resolution formally declaring independence from Great Britain. Two days later, on the Fourth of July, the Declaration of Independence was adopted and publicly released. Victory in the 1775–1783 Revolutionary War brought international recognition of the country's sovereignty.
The U.S. rapidly expanded its territory westward by purchasing, settling and conquering various areas controlled by Europeans and Indigenous peoples. As more states were admitted into the Union, a North–South division over slavery led 11 Southern states to declare secession and join as the Confederate States of America in order to preserve slavery there. These states fought against the Union in the American Civil War of 1861–1865 and were defeated. With the United States' victory and reunification, slavery was abolished nationally.
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 1941, the U.S. entered World War II on the side of the Allies. The war's aftermath left the U.S. and the Soviet Union as rival superpowers, competing for ideological dominance and international influence during the Cold War. The Soviet Union's collapse in 1991 left the U.S. as the world's sole superpower, although China has been widely cited since the 2020s as potentially achieving the same status.
The federal government is a representative democracy with a president and a constitution that creates a separation of powers among three branches: legislative, executive, and judicial. The Congress is 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 grants substantial autonomy to the 50 states.
A developed country, the U.S. ranks high in economic competitiveness, innovation, and higher education. Accounting for over a quarter of nominal global GDP, its economy has been the world's largest since about 1890. It is the wealthiest country, with the highest disposable household income per capita among OECD members, though its wealth inequality is highly pronounced. Shaped by centuries of immigration, the culture of the U.S. is diverse and globally influential. Making up nearly a third of global military spending, the country is widely considered to have the most powerful armed forces in the world and was the first to develop and employ nuclear weapons. A member of numerous international organizations including the United Nations Security Council, it plays a major role in global political, cultural, economic, and military affairs.
Documented use of the phrase "United States of America" dates back to January 2, 1776. On that day, Stephen Moylan, a Continental Army aide to General George Washington, wrote a letter to Joseph Reed, Washington's aide-de-camp, seeking to go "with full and ample powers from the United States of America to Spain" to seek assistance in the Revolutionary War effort. The first known public usage is an anonymous essay published in the Williamsburg newspaper The Virginia Gazette on April 6, 1776. Sometime on or after June 11, 1776, Thomas Jefferson wrote "United States of America" in a rough draft of the Declaration of Independence, which was adopted by the Second Continental Congress on July 4, 1776.
The term "United States" and its initialism "U.S.", used as nouns or as adjectives in English, are common short names for the country. The initialism "USA", a noun, is also common. "United States" and "U.S." are the established terms throughout the U.S. federal government, with prescribed rules. "The States" is an established colloquial shortening of the name, used particularly from abroad; "stateside" is the corresponding adjective or adverb.
"America" is the feminine form of the first name of Americus Vesputius, the Latinized name of Italian explorer Amerigo Vespucci (1454–1512); it was first used as a place name by the German cartographers Martin Waldseemüller and Matthias Ringmann in 1507. Vespucci proposed that the West Indies discovered by Christopher Columbus in 1492 were part of a previously unknown landmass and not among the Indies at the eastern limit of Asia. In English, the term "America" (used without a qualifier) seldom refers to topics unrelated to the United States. "The Americas" is the general term to describe the totality of the continents of North and South America.
The first inhabitants of North America migrated from Siberia approximately 15,000 years ago, either across the Bering land bridge or along the now-submerged Ice Age coastline. The Clovis culture, which appeared around 11,000 BCE in North America, is believed to be the first widespread culture in the Americas. Over time, Indigenous North American cultures grew increasingly sophisticated, and some, such as the Mississippian culture, developed agriculture, architecture, and complex societies. In the post-archaic period, the Mississippian cultures were located in the midwestern, eastern, and southern regions, and the Algonquian in the Great Lakes region and along the Eastern Seaboard, while the Hohokam culture and Ancestral Puebloans inhabited the Southwest. Native population estimates of what is now the United States before the arrival of European colonizers range from around 500,000 to nearly 10 million.
European exploration, colonization and conflict (1513–1765)
Christopher Columbus began exploring the Caribbean for Spain in 1492, leading to Spanish-speaking settlements and missions from what are now Puerto Rico and Florida to New Mexico and California. The first Spanish colony in the present-day continental United States was Spanish Florida, chartered in 1513. After several settlements failed there due to starvation and disease, Spain's first permanent town, Saint Augustine, was founded in 1565.
France established its own settlements in French Florida in 1562, but they were either abandoned (Charlesfort, 1578) or destroyed by Spanish raids (Fort Caroline, 1565). Permanent French settlements were founded much later along the Great Lakes (Fort Detroit, 1701), the Mississippi River (St. Louis, 1764) and especially the Gulf of Mexico (New Orleans, 1718). Early European colonies also included the thriving Dutch colony of New Nederland (settled 1626, present-day New York) and the small Swedish colony of New Sweden (settled 1638 in what became Delaware). British colonization of the East Coast began with the Virginia Colony (1607) and the Plymouth Colony (Massachusetts, 1620).
The Mayflower Compact in Massachusetts and the Fundamental Orders of Connecticut established precedents for local representative self-governance and constitutionalism that would develop throughout the American colonies. While European settlers in what is now the United States experienced conflicts with Native Americans, they also engaged in trade, exchanging European tools for food and animal pelts. Relations ranged from close cooperation to warfare and massacres. The colonial authorities often pursued policies that forced Native Americans to adopt European lifestyles, including conversion to Christianity. Along the eastern seaboard, settlers trafficked Africans through the Atlantic slave trade, largely to provide manual labor on plantations.