The state highway runs 53.31 miles (85.79 km) from U.S. Route 221 (US 221) in Hillsville north to SR 61 in Narrows.

SR 100 passes through the hamlet of Sylvatus before entering Wythe County and crossing Little Reed Island Creek.

The roadway continues north as US 11 (Lee Highway) across the mountain to Pulaski; US 11 also heads south along I-81 toward Wytheville.

Just north of the rail spur, the state highway enters the town of Dublin, where it crosses over Norfolk Southern Railway's Pulaski District rail line immediately before a partial cloverleaf interchange with US 11 (Lee Highway) adjacent to the main campus of New River Community College.

In the center of town, SR 100 intersects US 460 Business (Wenonah Avenue) and runs concurrently with the U.S. Highway on Main Street through downtown.