South Carolina Highway 421
| Augusta Road | ||||
| Route information | ||||
| Maintained by SCDOT | ||||
| Length | 10.360 mi (16.673 km) | |||
| Existed | 1952–present | |||
| Major junctions | ||||
| South end | US 1 / US 78 / US 278 / SC 125 southwest of Clearwater | |||
| North end | US 1 / US 78 in Aiken | |||
| Location | ||||
| Country | United States | |||
| State | South Carolina | |||
| Counties | Aiken | |||
| Highway system | ||||
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South Carolina Highway 421 (SC 421) is a 10.360-mile (16.673 km) state highway in the U.S. state of South Carolina. It is an alternate route to U.S. Route 1 (US 1) and US 78 between North Augusta and Aiken.