Dauphin County // is a county in the U.S. state of Pennsylvania and is one of the three counties comprising the Harrisburg–Carlisle Metropolitan Statistical Area. As of 2010 census, the population was 268,100. The county includes the city of Harrisburg, which has served as the state capital since 1812. Also located within the county is Three Mile Island Nuclear Generating Station, site of the 1979 nuclear core meltdown.
Dauphin 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 Louis XVI. Louis-Joseph's title of Dauphin signified that he was the heir apparent to the throne of France. The county seat is Harrisburg, Pennsylvania's capital and tenth largest city.