Duncannon is a borough in Perry County, Pennsylvania, United States.

In his journal he describes his trip on the Susquehanna and his brief stay with an Indian tribe on Duncan's Island, across the river from present-day Duncannon.

[11] According to the U.S. Census Bureau, the borough has a total area of 0.4 square miles (1.0 km2), all land.

36.1% of all households were made up of individuals, and 16.8% had someone living alone who was 65 years of age or older.

On S. Market Street, there is a mural with various artistic depictions of life and scenery in Duncannon, the entire area that is Perry County, Pennsylvania as a whole, and even of the entire United States.

A high percentage of the population is Christian, and many churches are in Duncannon, including a Lutheran,[15] UCOC, Assembly of God, Presbyterian, Catholic, and Church of God.