Dam Number 5

The Confederates attempted to damage Dam Number 5 on the Chesapeake and Ohio Canal in June 1861, and three more times between December 1861 and early January 1862.

Dam Number 5, located seven miles above Williamsport, was the fifth of seven dams built in the Potomac River to impound and divert water from the river into the Chesapeake and Ohio Canal. The dam was built of cribs, which were hollow cages built of heavy timbers that were anchored to the riverbed, filled with rock and sheeted with planks. Construction of the dam commenced March 1833 and was completed in December 1834. A series of floods in 1857 seriously damaged Dam Number 5, at one point washing out 500 feet of the structure. Temporary repairs were made, but financial difficulties prevented the canal company from undertaking permanent restoration of the dam prior to the Civil War.

Before evacuating Harpers Ferry in June 1861, Confederate Gen. Joseph E. Johnston sent work parties to the Potomac to breech Dam Number 5, hoping to disable the canal prior to his evacuation of Harpers Ferry. On June 8 the Confederates set off a powder charge in the dam and over the next two days skirmished with the Clear Spring and Williamsport home guards. No significant damage was done to the dam.

In December 1861 and early 1862 troops from Confederate Gen. Thomas J. “Stonewall” Jackson’s command made a series of attempts to disable Dam Number 5. From December 6–8 a force led by Turner Ashby attempted to cut the cribs and to dig a trench to divert water around the southern abutment of the dam. Strong defensive positions and heavy fire from Union infantry forced Ashby to abandon the undertaking. From December 17–20 Jackson accompanied his brigade to the Potomac for another attempt to damage the dam. Demonstrations were made against Falling Waters and Williamsport and a work detail attempted to cut the cribs after dark. All attempts to inflict damage to the dam were unsuccessful until the last night when Jackson sent a sizable portion of his force upriver with boats. The Union defenders followed, which gave Jackson’s men an evening to work without detection. When the work party heard timber cracking, they assumed they had made a significant breech. Jackson left the river, but soon learned that canal navigation had resumed. On January 1 a small force under Ashby arrived at the dam again, where they spend two more nights widening the breach. The damage to the dam was not significant enough to halt navigation on the waterway, although a serious winter flood in late January accomplished the task for Jackson.