United States, officially United States of America, abbreviated U.S. or U.S.A., byname America, country in North America, a federal republic of 50 states. Besides the 48 conterminous states that occupy the middle latitudes of the continent, the United States includes the state of Alaska, at the northwestern extreme of North America, and the island state of Hawaii, in the mid-Pacific Ocean.
At 3.8 million square miles (9.8 million square kilometers), it is the world's third- or fourth-largest country by total area. With a population of more than 331 million people, 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.