 The Dusmal House and Mingo Creek Presbyterian Church and Churchyard are listed on the National Register of Historic Places.According to the United States Census Bureau, the township has a total area of 15.7 square miles (40.8 km²), of which, 15.4 square miles (39.8 km²) of it is land and 0.4 square miles (1.0 km²) of it (2.41%) is water.Union Township has five land borders, including South Park Township and Jefferson Hills (both in Allegheny County) to the north, Carroll Township to the south, and Nottingham and Peters Townships to the west.