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.

Paleo-Indians migrated from North Asia to North America over 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. Subsequent 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.