It was established January 3, 1815 and named Union as it was formed from parts of Deerfield and Turtlecreek Townships.

[4] The township is governed by a three-member board of trustees, who are elected in November of odd-numbered years to a four-year term beginning on the following January 1.

Interstate 71 crosses the township from southwest to northeast and State Route 48 from south to north.

Formerly, the Middletown and Cincinnati Railroad crossed the township, but all track southeast of US 42 has been abandoned and lifted.

The city of Lebanon's sewage treatment plant is in Union Township, along the Little Miami River.