Boston is located within a constitutional federal republic.
Boston ( pronounced [ ˈbɒstən ] ) is the capital and most populous city of the Commonwealth of Massachusetts in the United States . Alternately , as a Combined Statistical Area ( CSA ) , this wider commuting region is home to some 8.1 million people , making it the sixth-largest as such in the United States . The United States of America ( USA ) , commonly known as the United States ( U.S. ) or America , is a constitutional federal republic composed of 50 states , a federal district , five major self-governing territories , and various possessions . Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico .