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 . The city proper covers 48 mi2 with an estimated population of 667,137 in 2015 , making it the largest city in New England and the 23rd most populous city in the United States . One of the oldest cities in the United States , Boston was founded on the Shawmut Peninsula in 1630 by Puritan settlers from England . 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 .