The United States of America (USA), commonly known as the United States or America, is a country mostly located in central North America, between Canada and Mexico. It consists of 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, it is the world's third- or fourth-largest country by total area. With a population of over 328 million, it is the third most populous country in the world. The federal capital is Washington, D.C., and the most populous city is New York City.