Mill Run is a 9.1-mile-long (14.6 km)[1] tributary stream of the South Branch Potomac River, belonging to the Potomac River and Chesapeake Bay watersheds.
[2] The stream is located in Hampshire County in the Eastern Panhandle of the U.S. state of West Virginia.
The stream runs northeast, then northwest, where it is met with a number of trails and old lumbering roads used by fishermen and hunters that utilize the WMA.
Two small unnamed streams also born from hollows in Nathaniel Mountain join Mill Run as it flows toward Peterkin Conference Center.
After passing through Peterkin, Mill Run adjoins Hampshire Park and its 4-H camp facilities such as its council circle and makes its way past the old Pancake Schoolhouse.