The United States of America (USA or U.S.A.), commonly known as the United States (US or U.S.) or America, is a country primarily located in North America. It is a federal union of 50 states, which also includes its federal capital district of Washington, D.C., and 326 Indian reservations. The 48 contiguous states are bordered by Canada to the north and Mexico to the south. The State of Alaska is non-contiguous and lies to the northwest, while the State of Hawaii is an archipelago in the Pacific Ocean. The United States also asserts sovereignty over five major unincorporated island territories and various uninhabited islands. The country has the world's third-largest land area, second-largest exclusive economic zone, and third-largest population, exceeding 334 million.

Paleo-Indians migrated across the Bering land bridge more than 12,000 years ago, and went on to form various civilizations and societies. British colonization led to the first settlement of the Thirteen Colonies in Virginia in 1607. 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. Following its victory in the 1775–1783 Revolutionary War, the country continued to expand across North America.