The United States of America , commonly known as the United States or informally America, is the most populous country in North America. It consists of 50 states, a federal district, five major unincorporated territories, nine Minor Outlying Islands, and 326 Indian reservations. It is the third-largest country by both land and total area. The United States shares land borders with Canada to its north and with Mexico to its south. It has maritime borders with the Bahamas, Cuba, Russia, and other nations. With a population of over 331 million, it 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.