what county is duncannon pa
Homefacts City Report. Duncannon is located in Perry County, PA. The population is 1,578, making Duncannon the 2nd largest city in Perry County. There are 3 public schools in Duncannon with an average Homefacts rating of C. The total crime rate for Duncannon is low, and there are 12 registered sex offenders residing in the city.