Millerstown is an unincorporated community in eastern Johnson Township, Champaign County, Ohio, United States. It lies at the intersection of Heck Hill, Ward, and Zimmerman Roads, 2+1/2 mi north of U.S. Route 36. Nettle Creek, a tributary of the Mad River, flows past Millerstown. It is located approximately 4 miles (6½ km) northeast of the city of St. Paris and 10 mi west-northwest of the city of Urbana, the county seat of Champaign County.

History

Millerstown was platted in 1837. The community was named for early landowner Casper Miller. A post office was established at Millerstown in 1838, and remained in operation until 1903.