Delaware County
Also known as Delaware County, Pennsylvania, Delaware County, PA, Delco
county in Pennsylvania, United States
Key facts
- Country
- United States
- State
- Pennsylvania
- Founded
- September 26, 1789
- Named after
- Delaware River
- Seat
- Media
- Largest township
- Upper Darby
- Other cities
- Chester
- Total
- 191 sq mi (490 km )
- Land
- 184 sq mi (480 km )
- Water
- 6.8 sq mi (18 km ) 3.5%
- Estimate 2025
- 580,937
- Density
- 3,130/sq mi (1,210/km )
- Congressional district
Article
Delaware County, colloquially referred to as Delco, is in the Commonwealth of Pennsylvania. With a population of 576,830 as of the 2020 census, it is the fifth-most populous county in Pennsylvania and the third-smallest in area. The county was created on September 26, 1789, from part of Chester County and named for the Delaware River. The county is part of the Philadelphia metropolitan area, or Delaware Valley, region of the commonwealth.
Delaware County borders Philadelphia, the nation's sixth-most populous city, to its northeast. It also is adjacent to the city-county of Philadelphia County and is included in the Philadelphia–Camden–Wilmington, PA–NJ–DE–MD metropolitan statistical area. Its county seat is Media, which is located near the center of the county.