Hanover Township was the 12th township formed. It was approved Dec. 2, 1811, by Butler County commissioners. Its was taken from Reily and St. Clair townships. It was one of three townships formed in 1811, including Morgan Township March 4 and Oxford Township Aug. 5. The township took its name from the village of Hanover in Hanover County in Virginia, the home of Patrick Henry and Henry Clay.