 At Stone Creek north of the gap, US 421 meets the southern end of SR 352 (St. Charles Road), which serves the town of St. Charles to the north.The U.S. Highway heads west, following Stone Creek to its source near the Kentucky state line, which coincides with the Tennessee Valley Divide, from which US 421 continues northwest toward Harlan.The majority of US 421 in Virginia, from Pennington Gap east to Bristol, was designated as part of State Route 10 in 1918; the rest was not a state highway until the late 1920s.