Shenandoah valley, part of the Great Valley of the Appalachians, c.150 mi (240 km) long, N Va., located between the Blue Ridge and the Allegheny mts. The valley is divided into two parts by Massanutten Mt., a ridge c.45 mi (70 km) long and c.3,000 ft (915 m) high. The Shenandoah River, c.150 mi (240 km) long, rises in two forks on either side of the ridge, uniting near Front Royal, Va., and flowing northeast to enter the Potomac at Harpers Ferry, W.Va. The Shenandoah valley was first explored in the early 1700s. The valley was an important corridor in the westward pioneer movement, and it became a rich agricultural area with farm-land, orchards, and pastures. During the Civil War, the valley was the ideal avenue of approach for the Southern invasion of the North, and it served as one of the Confederates' principal storehouses. Shenandoah figured in the "valley campaign" of Stonewall Jackson in 1862; Lee retreated through the valley after being checked in the Antietam campaign (1862) and the Gettysburg campaign (1863). By early 1865, the valley was completely lost to the South. The principal cities are Winchester, Front Royal, Staunton, and Waynesboro. The many recreational areas include Shenandoah National Park, in the surrounding uplands.