quality:corruption, structural:reformatting
Philadelphia, colloquially referred to as Philly, is the most populous city in the U.S. state of Pennsylvania and the sixth-most populous city in the United States, with a population of 1,603,797 in the 2020 census. The city is the urban core of the larger Delaware Valley, also known as the Philadelphia metropolitan area, the eighth-largest metropolitan region in the nation with 6.245 million residents in its metropolitan statistical area, and 7.366 million residents in its combined statistical area.

Philadelphia has played an extensive role in United States history. The city was founded in 1682 by William Penn, an English Quaker and advocate of religious freedom. The city served as the capital of the Pennsylvania Colony during the British colonial era and went on to play a historic and vital role as the central meeting place for the nation's founding fathers during the American Revolution and subsequent Revolutionary War. Philadelphia hosted the First Continental Congress in 1774, preserved the Liberty Bell, and hosted the Second Continental Congress during which the nation's 56 founders formed the Continental Army and elected George Washington as its commander in 1775, and unanimously adopted the Declaration of Independence on July 4, 1776. For nine months, from September 1777 to June 1778, the city fell under British occupation during the war's Philadelphia campaign. In 1787, the U.S. Constitution was ratified in Philadelphia at the Philadelphia Convention. Philadelphia remained the nation's largest city until 1790, and it served as the nation's first capital from May 10, 1775, until December 12, 1776, and on four subsequent occasions until 1800, when construction of the new national capital in Washington, D.C. was completed.

Philadelphia maintains extensive contemporary influence in business and industry, culture, sports, and music. With 17 four-year universities and colleges in the city, Philadelphia is one of the nation's leading centers for higher education and academic research. The city is a national cultural center, hosting more outdoor sculptures and murals than any other city in the nation. Fairmount Park, when combined with adjacent Wissahickon Valley Park in the same watershed, is 2,052 acres (830 ha), representing one of the nation's largest and the world's 54th-largest urban park. Philadelphia is known for its arts, culture, cuisine, and colonial and Revolutionary-era history; in 2016, it attracted 42 million domestic tourists who spent $6.8 billion, representing $11 billion in economic impact to the city and its surrounding Pennsylvania counties. With five professional sports teams and one of the nation's most loyal and passionate fan bases, Philadelphia is often ranked as the nation's best city for professional sports fans. The city has a culturally and philanthropically active LGBTQ+ community. Philadelphia also has played an immensely influential historic and ongoing role in the development and evolution of American music, especially R&B, soul, and rock.

As of 2022, the Philadelphia metropolitan area had a gross metropolitan product of US$518.5 billion and is home to five Fortune 500 corporate headquarters. Metropolitan Philadelphia ranks as one of the Big Five U.S. venture capital hubs, facilitated by its geographic proximity to both the entrepreneurial and financial ecosystems of New York City and to the federal regulatory environment of Washington, D.C. The Philadelphia Stock Exchange, owned by Nasdaq since 2008, is the nation's oldest stock exchange and a global leader in options trading. 30th Street Station, the city's primary rail station, is the third-busiest Amtrak hub in the nation, and the city's multimodal transport and logistics infrastructure also includes Philadelphia International Airport, a major transatlantic gateway and transcontinental hub, and the rapidly-growing PhilaPort seaport.

Philadelphia is a city of many firsts, including the nation's first library (1731), hospital (1751), medical school (1765), national capital (1774), university (by some accounts) (1779), central bank (1781), stock exchange (1790), zoo (1874), and business school (1881). Philadelphia contains 67 National Historic Landmarks, including Independence Hall. From the city's 17th century founding through the present, Philadelphia has been the birthplace or home to an extensive number of prominent and influential Americans. In 2021, Time magazine named Philadelphia one of the world's greatest 100 places. Two years later, in 2023, travel guide publisher Lonely Planet ranked Philadelphia the best city in the nation to visit.