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—a region located in the Northeastern United States at the confluence of the Delaware and Schuylkill Rivers with 7.2 million people residing in the eighth-largest combined statistical area in the United States.
The area's many universities and colleges make Philadelphia a top international study destination, as the city has evolved into an educational and economic hub. With a gross domestic product of $388 billion, Philadelphia ranks ninth among world cities and fourth in the nation. Philadelphia is the center of economic activity in Pennsylvania and is home to five Fortune 1000 companies. The Philadelphia skyline is growing, with a market of almost 81,900 commercial properties in 2016 including several nationally prominent skyscrapers. The city is known for its arts, culture, and rich history, attracting over 41 million domestic tourists alone in 2015. Philadelphia has more outdoor sculptures and murals than any other American city. Fairmount Park, when combined with the adjacent Wissahickon Valley Park in the same watershed, is one of the largest contiguous urban park areas in the United States. 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 U.S. firsts, including the first library (1731), first hospital (1751) and medical school (1765), first Capital (1777), first stock exchange (1790), first zoo (1874), and first business school (1881). Philadelphia is the only World Heritage City in the United States.