Dauphin County, Pennsylvania

Dauphin County
Location within the U.S. state of Pennsylvania
Pennsylvania's location within the U.S.
Coordinates: 40°25′N 76°47′W / 40.41°N 76.79°W / 40.41; -76.79
Country United States
State Pennsylvania
FoundedMarch 4, 1785
Named afterLouis Joseph, Dauphin of France
SeatHarrisburg
Largest townshipLower Paxton Township
Area
  Total
558 sq mi (1,450 km2)
  Land525 sq mi (1,360 km2)
  Water33 sq mi (90 km2)  5.9%
Population
 (2020)
  Total
289,234
  Estimate 
(2023)
289,234
  Density520/sq mi (200/km2)
Time zoneUTC−5 (Eastern)
  Summer (DST)UTC−4 (EDT)
Congressional district10th
Websitewww.dauphincounty.gov
DesignatedDecember 9, 1982

Dauphin County (/ˈdɔːfɪn/; Pennsylvania Dutch: Daffin Kaundi) is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 286,401. The county seat is Harrisburg, Pennsylvania's state capital and ninth-most populous city. The county was created on March 4, 1785, from part of Lancaster County and was named after Louis Joseph, Dauphin of France, the first son of King Louis XVI. Dauphin County is included in the Harrisburg–Carlisle Metropolitan Statistical Area. Located within the county is Three Mile Island Nuclear Generating Station, site of the 1979 nuclear core meltdown. The nuclear power plant closed in 2019. The county is part of the South Central region of the commonwealth.