 The highways curve north and parallel the Clinch River to Clinchport, where the road meets the southern end of SR 65 and begins to follow Stock Creek.US 421, US 23, and US 58 pass by Glenita, where the railroad splits north to pass through the Natural Tunnel, the centerpiece of Natural Tunnel State Park.After passing through the Devil's Racepath, US 58 and US 421 split west from US 23 (Orby Cantrell Highway) as Daniel Boone Trail just south of the town of Duffield.