[3] Located in the northeastern corner of the county, it borders the following townships: No municipalities are located in Sullivan Township, although the unincorporated community of Sullivan is located in the center of the township.

Sullivan Township was organized in 1819 as part of Medina County, and then became part of Lorain County in December 1822.

[4] It was added to Ashland County when it was formed on February 24, 1846 from portions of Huron, Lorain, Richland, and Wayne counties.

[6] 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,[7] 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.