Philadelphia is the largest city in the Commonwealth of Pennsylvania and the sixth-most populous city in the United States, with an estimated population of 1,567,872 and more than 6 million in the seventh-largest metropolitan statistical area, as of 2016. Philadelphia is the economic and cultural anchor of the Delaware Valley, located along the lower Delaware and Schuylkill Rivers, within both the Mid-Atlantic region and the Northeast megalopolis. The Delaware Valley's population of 7.2 million ranks it as the eighth-largest combined statistical area in the United States.William Penn, an English Quaker, founded the city in 1682 to serve as capital of the Pennsylvania Colony. Philadelphia played an instrumental role in the American Revolution as a meeting place for the Founding Fathers of the United States, who signed the Declaration of Independence in 1776 at the Second Continental Congress, and the Constitution at the Philadelphia Convention of 1787.