United States of America (U.S.A or US) is a constitutional federal republic comprising 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. The state of Alaska is in the northwest of the continent, with Canada to its east and Russia to the west across the Bering Strait, and the state of Hawaii is an archipelago in the mid-Pacific. The United States also possesses several territories, or insular areas, scattered around the Caribbean and Pacific.The United States is a federal union of fifty states. The original thirteen states were the successors of the thirteen colonies that rebelled against British rule. Most of the rest have been carved from territory obtained through war or purchase by the U.S. government. The exceptions are Vermont, Texas, and Hawaii; each was an independent republic before joining the union. Early in the country's history, three states were created out of the territory of existing ones: Kentucky from Virginia; Tennessee from North Carolina; and Maine from Massachusetts. West Virginia broke away from Virginia during the American Civil War. The most recent state, Hawaii, achieved statehood on August 21, 1959. The U.S. Supreme Court has ruled that the states do not have the right to secede from the union.
The states compose the vast bulk of the U.S. land mass; the only other areas considered integral parts of the country are the District of Columbia, the federal district where the capital, Washington, is located; and Palmyra Atoll, an uninhabited but incorporated territory in the Pacific Ocean. The United States possesses five major territories with indigenous populations: Puerto Rico and the United States Virgin Islands in the Caribbean; and American Samoa, Guam, and the Northern Mariana Islands in the Pacific. Those born in the territories (except for American Samoa) possess U.S. citizenship.