The borough of Corsica, a separate municipality, lies along the county line and is bordered to the north, east, and south by Union Township.

Interstate 80 crosses Union Township, with access from Exit 73 just north of Corsica.

U.S. Route 322 runs south of and parallel to I-80, passing through Corsica and Roseville.

[4] The township is bordered to the north by Mill Creek, a westward-flowing tributary of the Clarion River.

20.7% of all households were made up of individuals, and 9.3% had someone living alone who was 65 years of age or older.