The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a transcontinental country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territories, nine minor outlying islands, and 326 Indian reservations with limited sovereignty. It is the third-largest country by both land and total area. The United States shares land borders with Canada to the north and with Mexico to the south as well as maritime borders with the Bahamas, Cuba, and Russia, among others. It has a population of over 331 million, and is the third most populous country in the world. The national capital is Washington, D.C., and the most populous city and financial center is New York City. The United States is a melting pot of cultures and ethnicities, and its population has been profoundly shaped by centuries of immigration. It has a highly diverse climate and geography and is officially recognized as one of the 17 ecologically megadiverse countries.
