The United States of America, also known as the United States, the U.S., the U.S.A., the U.S. of A, the States, and America, is a country in North America. A federal republic, the United States shares land borders with Canada and Mexico, and extends from the Atlantic Ocean to the Pacific Ocean. Its capital is Washington, D.C.

The present-day continental United States has been inhabited for at least 15,000 years by Native Americans. After 16th-century European exploration and settlement, the English established new colonies, and gained control of others, in the eastern portion of the continent in the 17th and early 18th centuries. On 4 July 1776, at war with Britain over fair governance, thirteen of these colonies declared their independence; in 1783, the war ended in British acceptance of the new nation. Since then, the country has more than quadrupled in size: it now consists of 50 states, one federal district, and a number of overseas territories.

At over 3.7 million square miles (over 9.1 million km²), the U.S. is the third largest country by area. It is also the world's third most populous nation, with nearly 300 million people.