Boston is the capital and most populous city of the U.S. state of Massachusetts. It serves as a cultural and financial center of New England, a region of the Northeastern United States. Boston has an area of 48.4 square miles (125 km2) and a population of 675,647 as of the 2020 census, making it the third-most populous city in the Northeastern United States after New York City and Philadelphia. The larger Greater Boston metropolitan statistical area had a population of 5 million in 2025, making it the largest metropolis in New England and the eleventh-largest in the United States.