Union Township is one of eleven townships of Warren County, Ohio, located in the central part of the county. It is bounded on the south by the Little Miami River and across the river by Hamilton Township; on the east by Salem Township; on the north by Turtlecreek Township; on the west and south by Deerfield Township. It was established January 3, 1815 and named Union as it was formed from parts of Deerfield and Turtlecreek Townships. The 2000 census found 4,668 people in the township, up slightly from the 4,631 in 1990. Of those, 2,230 lived in the unincorporated part of the township and 2,438 lived in the village of South Lebanon.

The smallest township in the county, it originally had fifteen full and six fractional sections of land totalling 11,970 acres. However, a large portion of the township has been annexed into South Lebanon, Lebanon, and Mason. The village of South Lebanon remains within the township, but Mason and Lebanon are not and that land has been lost. The township is prone to flooding from the Little Miami and Turtle Creek.

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. Two are elected in the year after the presidential election and one is elected in the year before it. There is also an elected township clerk, who serves a four-year term beginning on April 1 of the year after the election, which is held in November of the year before the presidential election. Vacancies in the clerkship or on the board of trustees are filled by the remaining trustees.

The entire township is in the Symmes Purchase and was surveyed in accordance with the unusual plan Symmes chose.

There is significant gravel mining in the township. Interstate 71 crosses the township from southwest to northeast and State Route 48 from south to north. US Route 42 clips the northwest corner of the township. Formerly, the Middletown and Cincinnati Railroad crossed the township, but all track southeast of US Route 42 has been abandoned and lifted. The city of Lebanon's sewage treatment plant is here, along the Little Miami River.

Most of the township is in the Kings Local School District, which was formerly known as the Deerfield-Union Local School District, while parts are in the Lebanon City School District, the Mason City School District, and the Little Miami Local School District.

Telephone service is provided through the South Lebanon, Lebanon, Mason, and Morrow exchanges, while the South Lebanon, Lebanon, Kings Mills, and Morrow post offices serve the township.

References

• Elva R. Adams. Warren County Revisited. [Lebanon, Ohio]: Warren County Historical Society, 1989.
• The Centennial Atlas of Warren County, Ohio. Lebanon, Ohio: The Centennial Atlas Association, 1903.
• John W. Hauck. Narrow Gauge in Ohio. Boulder, Colorado: Pruett Publishing, 1986. ISBN 0871086298
• Josiah Morrow. The History of Warren County, Ohio. Chicago: W.H. Beers, 1883. (Reprinted several times)
• Ohio Atlas & Gazetteer. 6th ed. Yarmouth, Maine: DeLorme, 2001. ISBN 0899332811
• William E. Smith. History of Southwestern Ohio: The Miami Valleys. New York: Lewis Historical Publishing, 1964. 3 vols.
• Warren County Engineer's Office. Official Highway Map 2003. Lebanon, Ohio: The Office, 2003.