Philadelphia (/ˌfɪləˈdɛlfiə/) is the largest city in the Commonwealth of Pennsylvania and its only consolidated city-county, the fifth-most-populous city in the United States, and the core of the sixth-largest metropolitan area in the country. Located in the Northeastern United States at the confluence of the Delaware and Schuylkill rivers, Philadelphia is the economic and cultural center of the Delaware Valley. The population of the city was counted at 1,526,006 in 2010 and estimated at 1,560,297 in 2014, according to the United States Census Bureau. The four Pennsylvania counties nearest Philadelphia had an estimated total population of 2,510,793 in 2013; while by 2014 census estimates, the Philadelphia metropolitan area, also known as the Delaware Valley, is home to 6.1 million residents, and the larger Philadelphia-Reading-Camden, PA-NJ-DE-MD Combined Statistical Area contains approximately 7.2 million residents.
In 1682, William Penn founded the city to serve as capital of the Pennsylvania Colony. During the American Revolution, Philadelphia played an instrumental role as a meeting place for the Founding Fathers of the United States, who signed the Declaration of Independence in 1776 and the Constitution in 1787. Philadelphia was one of the nation's capitals during the Revolutionary War, and the city served as the temporary U.S. capital while Washington, D.C., was under construction. During the 19th century, Philadelphia became a major industrial center and railroad hub that grew from an influx of European immigrants. It became a prime destination for African Americans during the Great Migration and surpassed two million occupants by 1950. Following numerous civil rights protests and riots, the city experienced decades of heavy crime and neared bankruptcy by the 1980s. Revitalization began in the 1990s, with gentrification turning around many neighborhoods and reversing its decades-long trend of population loss.
Philadelphia is the center of economic activity in Pennsylvania and is home to seven Fortune 1000 companies. The Philadelphia skyline is growing, with several nationally prominent skyscrapers. The city is known for its arts, culture, and history, attracting over 39 million domestic tourists in 2013. Philadelphia has more outdoor sculptures and murals than any other American city, and Fairmount Park is the largest landscaped urban park in the world. The 67 National Historic Landmarks in the city helped account for the $10 billion generated by tourism. Philadelphia is the birthplace of the United States Marine Corps, and is also the home of many US firsts, including the first library (1731), first hospital (1751) and medical school (1765), first Capitol (1777), first stock exchange (1790), first zoo (1874), and first business school (1881).