Duncannon is a borough in Perry County, Pennsylvania, United States. The population was 1,473 at the 2020 census. It is part of the Harrisburg–Carlisle Metropolitan Statistical Area. The center of population of Pennsylvania is located in Duncannon. Lightning Guider Sleds were manufactured in Duncannon from 1904 until 1988. The Appalachian Trail makes its way through the town, going on various streets, and runs mainly along North High Street.