The United States of America (USA), commonly known as the United States (US or U.S.) or America, is a country primarily located in central North America, between Canada and Mexico. It consists of 50 states, a federal district, five self-governing territories, and several other island possessions.^[h] At 3.8 million square miles (9.8 million square kilometers), it is the world's third- or fourth-largest country by total area.^[d] With a population of over 328 million, it is the third most populous country in the world. The national capital is Washington, D.C., and the most populous city is New York City.