Dauphin County () 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.
Geography
According to the U.S. Census Bureau, the county has a total area of , of which is land and (5.9%) is water. The county is bound to its western border by the Susquehanna River (with the exception of a small peninsula next to Duncannon). The area code is 717 with an overlay of 223.
Adjacent counties
- Northumberland County (north)
- Schuylkill County (northeast)
- Lebanon County (east)
- Lancaster County (south)
- York County (southwest)
- Cumberland County (west)
- Perry County (west)
- Juniata County (northwest)
Major roads and highways
- 25px SR 3032
Climate
Most of the county by area has a humid continental climate (Dfa except for some Dfb in highlands.) The inclusion of temperature numbers for the past decade shows some lower-lying areas, including Harrisburg, to have a humid subtropical climate (Cfa.) The hardiness zone is 7a except in some higher northern areas where it is 6b and a few very small areas along the river below the city including the airport where it is 7b. [https://planthardiness.ars.usda.gov/]