Philadelphia, city and port, coextensive with Philadelphia county, southeastern Pennsylvania, U.S. It is situated at the confluence of the Delaware and Schuylkill rivers. Area 135 square miles (350 square km). Pop. (2010) 1,526,006; Philadelphia Metro Division, 4,008,994; Philadelphia-Camden-Wilmington Metro Area, 5,965,343; (2020) 1,603,797; Philadelphia Metro Division, 2,180,627; Philadelphia-Camden-Wilmington Metro Area, 6,245,051.

Philadelphia has been described both as the elegant but rather jaded great lady and as the overage and sickly spinster of American cities. A more realistic look at Philadelphia, however, shows it to be a very modern and vigorous city, arising in gracious counterpoint to the deep serenity of an older city that has provided gentle but firm intellectual, economic, and humanitarian direction to the nation at whose birth it played midwife.