The township of Franklin lies in the southeast corner of Marion County, being bounded on the north and west respectively by the townships of Warren and Perry, on the south by Johnson County, and on the east by the counties of Shelby and Hancock. The township is traversed diagonally from southeast to northwest by the line of the Cincinnati, Indianapolis, St. Louis and Chicago Railway. The principal stream is Buck Creek, which enters the township across its north line a short distance west of its northeastern corner, flows through the eastern part of Franklin in a general southward direction, nearly parallel with the eastern line, and leaves the township at a point near its south eastern corner, joining its waters with those of Big Sugar Creek in Shelby County. Wild Cat and Indian Creeks, Big Run, and several smaller streams are tributaries of Buck Creek which flow in a south east wardly direction through Franklin Township to their junctions with the main stream.