The entire township is in the Symmes Purchase and was surveyed in accordance with the unusual plan Symmes chose. The township is prone to flooding from the Little Miami and Turtle Creek. The village of South Lebanon remains within the township, but Mason and Lebanon are not and that land has been lost. However, a large portion of the township has been annexed into South Lebanon, Lebanon, and Mason. The smallest township in the county, it originally had fifteen full and six fractional sections of land totaling 11,970 acres (48 km 2). Hamilton Township - south, across the Little Miami River.Located in the central part of the county, it borders the following townships:

The population was 6,251 as of the 2020 census.

It was established Januand named Union as it was formed from parts of Deerfield and Turtlecreek Townships. Vacancies in the fiscal officership or on the board of trustees are filled by the remaining trustees.Union Township is one of the eleven townships of Warren County, Ohio, United States, located in the central part of the county. There is also an elected township fiscal officer, 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. Two are elected in the year after the presidential election and one is elected in the year before it. 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. In 1833, Union Township contained two post offices, four churches, one saw mill, and two physicians. It is one of twenty-seven Union Townships statewide. Two incorporated villages are located in Union Township: New Concord in the northeast, and Norwich in the northwest.

Westland Township, Guernsey County - east.

Adams Township, Guernsey County - northeast corner.

Located on the eastern edge of the county, it borders the following townships: The 2020 census found 4,265 people in the township. Union Township is one of the twenty-five townships of Muskingum County, Ohio, United States.

Union township oh