Perry County is a county located in the U.S. state of Pennsylvania and is one of three counties comprising the Harrisburg–Carlisle Metropolitan Statistical Area. As of 2010, the population was 45,969. The center of population of Pennsylvania is located in Perry County, in the borough of Duncannon. Green Park, an incorporated village located in northeastern Tyrone Township, serves as Perry County’s midpoint between the Conococheague Mountain in the west and the Susquehanna River to the east.
Perry County, originally part of Cumberland County, was created in 1820 in part because residents did not want to travel over the mountain to Carlisle (the county seat of Cumberland County). Perry County's county seat is Bloomfield, which is sometimes called New Bloomfield. It was created on March 22, 1820, and was named after Oliver Hazard Perry, hero of the War of 1812, who had recently died.