This Township is situated in the extreme south-west corner of Lorain County, and is bounded as follows: on the north by Brighton Township; south, by Troy township, Ashland County; east, by Huntington township; and west, by New London township, Huron County.
The streams are the west branch of the Black River and its tributaries. The stream flows from near the southwest corner of the township, is joined by a small stream and continues a general northeast direction, until it turns to the northwest and flows across the northern township line.
Rochester Township was the last settled of any of the townships now comprised within the boundary lines of
Lorain County in 1827. On April 6, 1835 the first township elected officers were John Conant, Joseph Hadley and Nehemiah Tinker. M. L. Blair, clerk and Benjamin C. Perkins, treasurer.