South Dakota Highway 21
Map of South Dakota with SD 21 in red | ||||
| Route information | ||||
| Maintained by SDDOT | ||||
| Length | 9.470 mi (15.240 km) | |||
| Existed | 1926–present | |||
| Major junctions | ||||
| South end | SD 28 west of Lake Norden | |||
| North end | US 81 east of Hayti | |||
| Location | ||||
| Country | United States | |||
| State | South Dakota | |||
| Counties | Hamlin | |||
| Highway system | ||||
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South Dakota Highway 21 (SD 21) is a 9.470-mile (15.240 km) state highway in south-central Hamlin Countym South Dakota, that connects Lake Norden and Hayti.
SD 21 originally extended from the Nebraska state line to the North Dakota state line, completely concurrent with U.S. Route 81 (US 81). By the mid-1930s, only the current part of the highway remained.