HARPERS FERRY – THE IMPACT OF GEOLOGY AND MOUNTAINOUS TOPOGRAPHY ON MILITARY OPERATIONS DURING THE AMERICAN CIVIL WAR

Harpers Ferry, West Virginia lies at the boundary between the Blue Ridge and the Valley and Ridge Provinces of the Appalachian Mountains. It developed as a hydro-powered industrial community in the water gap at the confluence of the Potomac and Shenandoah Rivers. The site was chosen for one of two United States Armories and Arsenals in 1795; construction began in 1799. It became a major transportation hub when the Chesapeake & Ohio Canal and the Baltimore & Ohio Railroad where built in the 1830s.

A fining upward sequence of Lower Cambrian metasediments, which were folded as part of the Blue Ridge-South Mountain anticlinorium, has undergone differential erosion. The resultant mountainous terrain figured prominently in the Civil War. Although well suited for the development of hydro-power, the town frequently flooded and was found to be indefensible from attack. During the Civil War Harpers Ferry changed hands eight times.

The most significant attack took place during Lee’s September 1862 campaign to invade the north when the Union garrison at Harpers Ferry would have been in the rear of the advancing Confederate forces. As such, Lee divided his army and sent a portion to capture Harpers Ferry. General Thomas J. “Stonewall” Jackson used the topography to his advantage. Jackson waited while Confederate forces occupied Maryland Heights and Loudoun Heights. These two ridges, which constitute the water gap, are both underlain by resistant Weverton Formation quartzite. Surrounded by Confederate artillery on the high ground, the Union garrison surrendered on September 15th 1862, resulting in the largest capture of Union troops during the Civil War.