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.
Harpers Ferry is a historic town in Jefferson County, West Virginia, United States. It is situated at the confluence of the Potomac and Shenandoah rivers where the U.S. states of Maryland, Virginia and West Virginia meet. It is the easternmost town in West Virginia. The original, lower section of the town is located on a low-lying flood plain created by the two rivers and surrounded by higher ground. Historically, Harpers Ferry is best known for John Brown's raid on the Armory in 1859 and its role in the American Civil War.
The lower part of Harpers Ferry is located within Harpers Ferry National Historical Park. Most of the remainder, which includes the more highly populated area, is included in the separate Harpers Ferry Historic District. Two other National Register of Historic Places properties adjoin the town: the B & O Railroad Potomac River Crossing and St. Peter's Roman Catholic Church.
The Appalachian Trail Conservancy (ATC) headquarters is located in Harpers Ferry and the town is one of only a few through which the Appalachian Trail passes directly. Harpers Ferry is also an outdoor recreation destination. Popular activities include white water rafting, fishing, mountain biking, tubing, canoeing, hiking, zip lining, and rock climbing