Known as Mill Gap Road, the state highway runs 14.94 miles (24.04 km) from the West Virginia state line near Mill Gap, where the highway continues west as West Virginia Route 84 (WV 84), east to U.S. Route 220 (US 220) at Vanderpool.

The state highway passes through a pair of hairpin turns as it descends to Townsend Draft.

At the draft's mouth at Back Creek, SR 84 turns north and follows Back Creek to Mill Gap, where the highway turns east and follows East Back Creek through its water gap between Little Mountain and Lantz Mountain.

The state highway turns north and follows the valley through the hamlet of Mill Gap to Meadowdale.

There, SR 84 turns east and follows the Jackson River through Vanderpool Gap between Monterey Mountain and Back Creek Mountain to its eastern terminus at US 220 (Jackson River Road) in the hamlet of Vanderpool south of the Highland County seat of Monterey.