Philadelphia is a major city in the Commonwealth of Pennsylvania in the United States. Philadelphia is Pennsylvania's most populous city, the sixth most populous city in the U.S., and the second most populous city on the U.S. East Coast. The U.S. Constitution was ratified in Philadelphia at the Philadelphia Convention of 1787. Philadelphia remained the nation's largest city until 1790, when it was surpassed by New York City, and served as the nation's first capital from May 10, 1775, until December 12, 1776, and on four subsequent occasions during and following the American Revolution, including from 1790 to 1800 while the new national capital of Washington, D.C. was under construction.

Source: Wikipedia