Philadelphia (colloquially Philly) is Pennsylvania’s most populous city, with 1.6 million residents as of the 2020 census, and anchors the nation’s ninth-largest metropolitan area. Founded in 1682 by English Quaker William Penn as a haven for religious freedom, it played a pivotal role in the American Revolution: hosting the Continental Congresses, adopting the Declaration of Independence in 1776, and serving as the nation’s first capital until 1800. Today, Philadelphia is a powerhouse of higher education (17 universities), public art (the most outdoor murals and sculptures in the U.S.), and professional sports, consistently ranked a top city for passionate fans. Its 2023 metropolitan economy reached $557.6 billion, driven by 13 Fortune 500 headquarters, a biotech hub nicknamed “Cellicon Valley,” and the Philadelphia Stock Exchange (the nation’s oldest, now owned by Nasdaq). A transportation nexus, it boasts the third-busiest Amtrak hub (30th Street Station) and American Airlines’ largest transatlantic hub at its international airport. Known as a “city of firsts,” it launched the nation’s first library (1731), hospital (1751), medical school (1765), and many other historic innovations.