Flenner's Mill was built about 1840 by Andrew Flenner, who erected a new mill at the site of Joseph Hershey's mill in St. Clair Twp. on Four Mile Creek between the mouths of Cotton Run and Seven Mile Creek. In 1855 it was owned by Jonas Wehr. In 1836 there also was a Flenner's Mill on the Great Miami River north of present Woodsdale. It was operated by David Flenner.