North Mountain is a long Appalachian ridge crossing parts of West Virginia and Virginia for about 23.5 miles from the Potomac River to Green Spring, separating Back Creek Valley from the Shenandoah Valley. Skinners Gap divides it into a lower, more broken northern section and a higher southern span that reaches 1,306 feet at Roundtop near Arden. Other named points include Potato Hill, High Knob, and several gaps. The ridge also shaped local place names, including Back Creek, and has been known as Great Ridge and Little North Mountain. In the Cold War, Roundtop housed Cowpuncher, a Presidential Emergency Facility with microwave relay towers.