Dam #4 to Harpers Ferry

The Upper Potomac ranges from Harpers Ferry to the North Branch. The region is characterized by ridges and valleys and the foothills of the Appalachian Mountains. The C&O Canal follows the Maryland side of the river to Cumberland. 

The seven dams on the Potomac River were originally built to divert water into the canal. Dam #4 provided water for 22 miles of the canal, from Milepost 84.6 downstream to Milepost 62.3, just above Harpers Ferry. The water was regulated at the guard lock at Dam #4 to maintain a consistent level of water traveling at two miles per hour down the canal prism. For the past hundred years Dam #4 has also been capturing the water's power at a facility on the West Virginia side of the river. This hydro-electric gravity dam, built in 1913 and modified in 1994, is 20 feet tall and approximately 800 feet across. It uses a drive belt to transfer power from the river to the turbines. They in turn provide electric power to people in Washington County.