For other "River Knobs", see River Knobs (disambiguation). The River Knobs — formerly known as East Seneca Ridge — are a ridge and series of knobs in western Pendleton County, West Virginia, USA, along a stretch of the North Fork South Branch Potomac River. Although the Knobs (peak elevation: 2,854 ft) are dwarfed by Spruce Mountain to the west (peak: 4,840 ft) and by North Fork Mountain to the east (peak: 4,588 ft), they are notable for their series of prominent “razorback” ridges or “fins”. The largest and most famous of these blade-like crags is Seneca Rocks.