Philadelphia County
county in Pennsylvania, United States
Key facts
- Country
- United States
- State
- Pennsylvania
- Founded
- March 10, 1682
- Named after
- City of Philadelphia
- Seat
- Philadelphia
- Largest city
- Philadelphia
- Total
- 143 sq mi (370 km )
- Land
- 134 sq mi (350 km )
- Water
- 8.6 sq mi (22 km ) 6.0%
- Estimate 2025
- 1,574,281
- Density
- 11,969/sq mi (4,621/km )
- Time zone
- UTC−5 ( Eastern )
- Summer dst
Article
Philadelphia County is the most populous of the 67 counties of Pennsylvania and the 24th-most populous county in the nation. As of the 2020 census, the county had a population of 1,603,797. It is coextensive with Philadelphia, the nation's sixth-largest city. The county is part of the Southeast Pennsylvania region of the state.
Philadelphia County is one of the three original counties, along with Chester and Bucks counties, founded by William Penn in November 1682. Since 1854, the county has been coextensive with the City of Philadelphia, which is also its county seat. Philadelphia County is the core county in the Philadelphia-Camden-Wilmington Combined Statistical Area (PA-NJ-DE-MD, located along the lower Delaware and Schuylkill Rivers, within the Northeast megalopolis).