The United States of America (also referred to as the United States, the U.S., the USA, or America) is a federal constitutional republic comprising of fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. In the year 1959, the United States accepted their territories of Alaska and Hawaii as the 49th and 50th states respectively. The state of Alaska is in the northwest of the continent, with Canada to the east. The state of Hawaii is an archipelago in the mid-Pacific. After World War II the United States and the Soviet Union emerged as the world's two superpowers.