The 2020 census reported 3,652 people living in the township.

Located in the eastern part of the county, it borders the following townships: The village of South Vienna is located in the northern part of the township, and the unincorporated community of Plattsburgh lies at the center of the township.

[4] Statewide, the only other Harmony Township is located in Morrow County.

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.

There is also an elected township fiscal officer,[5] 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.