The west branch begins directly southwest of the city of Swartz Creek in Gaines Township. It then flows northeast through the city and then through Flint Township, where it meets the eastern branch at Bristol Road and I-69.
The western limb commences immediately south-southwest of the town of Swartz Creek in Gaines Township. It subsequently flows north-east through the city and then through Flint Township, where it encounters the eastern limb at Bristol Road and I-69.