[2] Part of Shikellamy State Park is in Union Township.

According to the United States Census Bureau, the township has a total area of 10.8 square miles (27.9 km2), all land.

As of the census[4] of 2000, there were 1,427 people, 547 households, and 427 families residing in the township.

There were 596 housing units at an average density of 55.4 per square mile (21.4/km2).

17.2% of all households were made up of individuals, and 6.4% had someone living alone who was 65 years of age or older.