Charles Mill is a reservoir located in central Ohio near the junction of State Routes 430 and 603. Charles Mill Lake is a quiet and enjoyable place for boating, camping, fishing, hunting, or hiking. The lake is located in both Richland County and Ashland County, with the dam located in Ashland County. This lake is located on the Black Fork of the Mohican River. …Charles Mill is a reservoir located in central Ohio near the junction of State Routes 430 and 603. Charles Mill Lake is a quiet and enjoyable place for boating, camping, fishing, hunting, or hiking. The lake is located in both Richland County and Ashland County, with the dam located in Ashland County. This lake is located on the Black Fork of the Mohican River. Many local residents refer to Chales Mill Lake as Mifflin Lake due to its proximity to Mifflin, Ohio. The lake primarily sees local use by nearby residents who fish or boat; the marina is accessible from St. Rt. 430.