The Dams

by Gary M. Petrichick

Virginia troops entered Harpers Ferry on the day following Virginia’s secession on April 17, 1861, but before they could take possession, the Union garrison burned their intended quest, the United States Armory located there. The town became a base for training Southern volunteers, and soon, a staging area for raids on the C&O Canal and the B&O Railroad to impair their usefulness to the Union army. Col. Thomas J. Jackson was assigned command on April 27, to be replaced by Brig. Gen. Joseph E. Johnston on May 15.

By June 1861, both shores of the Potomac River around Washington, and Cumberland, Maryland, were occupied by Union forces, protecting Dam Nos, 1, 2 and 8, but Dam Nos. 3, through 6 remained highly vulnerable. Dam Nos. 3 and 6 were constructed of rock filled cribs, Dam No. 4 had recently been rebuilt as a masonry structure, and Dam No. 5 was a combination of the two, being only partially rebuilt. Other than the new Dam No. 4, none of the dams needed a war, what with periodic floods washing away sections of the structures and droughts exacerbating the porous quality of the rubble construction. Nevertheless, the dams now had another destructive force to contend with and they didn’t have long to wait.

On June 8 the Virginia militia attempted to put "a blast into Dam No. 5." The Clearspring Guards were dispatched to the dam and drove off the rebels, but that night they returned with a cannon to defend those working to destroy the dam. An explosive charge was ignited, destroying a small part of one stone-filled crib, but no serious damage was done. Union reinforcements arrived from Williamsport in the morning and again drove off the rebels but skirmishing continued for almost a week.

Around mid-month the Virginians directed their efforts toward Dam No. 4, working at night by lantern to drill into the rock foundation to place explosives. Reportedly the work was supervised by Redmond Brown, the man who superintended the Dam’s construction and who now had sons in the Confederate army. Union companies from Boonsboro and Sharpsburg converged and drove the Confederates from the field. While this stopped the direct attempt to destroy the dam, the proximity of Southern troops forestalled repairs, specifically to the stop lock, and until the damage was repaired, a number of coal boats were stranded. With Union forces now in Cumberland to the west and nearing Williamsport to the east, Gen. Johnston feared being trapped at Harpers Ferry and pulled back to Winchester on June 15.

Meanwhile, Dam No. 1 was leaking badly, but a Union officer warned that no repairs should be made, and if they were, he would have the dam torn down! With friends like this ... ? There was relative calm until mid-October when Confederate cavalry set out from Romney, (West) Virginia, with orders to destroy Dam No. 6. While attempting to blow up the South Branch railroad bridge they were driven off by Union infantry, ending that threat to the dam. The lack of success in putting the canal out of commission led some Virginians, notably Representative Alexander R. Boteler, to ask President Jefferson Davis for an experienced commander to lead the local recruits. On November 5 Davis ordered the return of Jackson, now a Major General and "Stonewall" as a result of his Manassas success.

In early December Jackson determined to destroy Dam No. 5, choosing it for two reasons – the new masonry Dam No. 4 was closer to Frederick where a Union division was headquartered, plus it was possibly "the strongest of its kind in the country." On December 7 Confederates began pounding Dam No. 5 and houses on the Maryland shore with artillery. All buildings in range were hit but the dam was unharmed. The Union companies on site were armed with smoothbore muskets that were ineffective against the attackers across the Potomac. A boat dispatched for reenforcements returned that night with a company armed with long range rifled muskets. They were deployed behind trees and told to hold fire until ordered. When on the morning of December 8 the Confederate artillery, confident that they were still in no peril from the Federals, moved their pieces to the river’s edge and resumed their assault on the dam, the Union troops opened fire and drove the Confederates from their guns. Without sufficient troops or supporting artillery, the Federals were unable to capture the six abandoned guns which were withdrawn by the rebels that night. The next day the Confederates, covered by small-arms fire, began digging around the Virginia end of the dam abutment. By dark, water was coursing around the base of the dam and the work party was recalled. Thinking they had successfully disabled the dam, the Confederates returned to Winchester. As luck would have it the level of the Potomac was falling fast and the trench was soon dry.

Jackson mounted another attack on Dam No. 5 the night of December 17. After sending a brigade to feign a threat on Williamsport, his Stonewall Brigade moved onto the hills overlooking the dam. A work party was sent to the center of the dam and into the water to tear away the dam’s cribs. Their efforts escaped detection by Union sentinels till daybreak when a pitched battle took place. Confederate artillery drove the Federal riflemen from the scene but Union artillery arrived soon to drive off both the rebel artillery and the work party. They returned to renew their work on the nights of the 18th, 19th, and 20th when Union artillery and infantry again drove them off. Jackson, thinking the dam breached sufficient to cripple the canal withdrew his forces. The damage was not that extensive and army work parties assisted canal crews in repairing the dam so that navigation could be resumed on the 21st. Jackson’s final unsuccessful attempt to destroy Dam No. 5 with artillery was made on January 4, 1862.

While military assaults on the dams eased off for the balance of the conflict, those of Mother Nature continued as normal. Repairs to Dam No. 5 had not yet been completed by mid-May when high water caused it serious damage. During a period of severe drought in early August 1862, a leak in Dam No. 6 stopped traffic on the canal which would not had been the case had the damage done by the Confederates to the steam pump at South Branch the previous winter been repaired. In late August, heavy silt accumulations at Guard Lock No. 3 were delaying loaded boats. The gates at Guard Locks Nos. 3 and 4 were burned during the September 1862 Antietam invasion, and high water in late October again breached Dam No. 5. The dam was repaired by mid-November, giving full water on the entire canal.

The gates of Guard Lock No. 2 were destroyed during Gen. J. E. B. Stewart’s cavalry crossing at Rowsers Ford on the way to Gettysburg in late June 1863. They were replaced by the end of the month. Leaks were still plaguing Dam No. 5 in October 1864, and in early March 1865 a heavy flood tore logs from the dam’s cribs.

A November 1865 engineering study revealed that Dam Nos. 1 and 2 , being composed of brush and loose stones, needed repairs estimated at twenty-five thousand dollars. Dam No. 3 needed only ordinary repairs. (It is curious that Dam No. 3, being located at Harpers Ferry which changed hands between the Union and Confederacy eight times during the war, apparently went relatively unmolested by the combatants.) Dam No. 4 was in sound condition. Dam No. 5 was two thirds new with one third yet to be rebuilt. Dam No. 6 was in general good condition and Dam No. 8, exclusively stone, was in perfect order. Dam No. 7, due to the foresight of not having been built, escaped wartime damage.

Material drawn primarily from Harlan D. Unrau’s History of the C & O Canal

(This article was published in the June 2008 issue of Along The Towpath, the newsletter of the C&O Canal Association.)

Back to Civil War Series index