WV 51 begins at an intersection with WV 45 at Mills Gap on top of North Mountain in Berkeley County, where the road continues north as CR 20 (Buck Hill Road). From this intersection, WV 51 heads south as two-lane undivided Gerrardstown Road and descends the forested mountain. The road turns east-southeast at the base of the mountain and heads into the agricultural Shenandoah Valley. The route curves southeast and passes through the residential community of Gerrardstown. From here, WV 51 turns east and runs through a mix of farmland and woodland with some development. Farther east, the road heads into Inwood and turns northeast to reach a diamond interchange with I-81. Past this interchange, the route becomes a three-lane road with a center left-turn lane and passes businesses in the northern part of Inwood, crossing a Winchester and Western Railroad line. WV 51 comes to a roundabout with US 11 and heads southeast as the Inwood Bypass, reaching another roundabout before intersecting CR 51/20 (Middleway Pike) at a roundabout. At this point, the route heads southeast on two-lane undivided Middleway Pike and passes through a mix of residential and commercial areas. The road leaves Inwood and continues south-southeast through a mix of fields, woods, and development, curving to the southeast and passing through the community of Tarico Heights.
