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 between Canada and Mexico. It is a federation of 50 states a federal capital district (Washington D.C.) and 326 Indian reservations. Outside the union of states it asserts sovereignty over five major unincorporated island territories and various uninhabited islands. The country has the world's third-largest land area largest maritime exclusive economic zoneand the third-largest population exceeding 334 million.