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| U.S. Route 21 (South Carolina) | |
|---|---|
| State | SC |
| Type | US |
| Route | 21 |
| Length mi | 143.7 |
| Established | 1926 |
| Direction a | South |
| Terminus a | Charleston |
| Direction b | North |
| Terminus b | Yemassee |
| Counties | Charleston County, Berkeley County, Dorchester County, Colleton County, Beaufort County |
U.S. Route 21 (South Carolina) is a United States Numbered Highway running through the southeastern part of South Carolina, linking the Atlantic coastal region with inland corridors near the Savannah River Basin and the Sea Islands. The route connects multiple municipalities, military installations, and historic districts, providing a north–south arterial function that complements Interstate corridors and state highways. U.S. Route 21 traverses landscapes ranging from urban Charleston neighborhoods to rural Lowcountry farmland and tidal wetlands.
U.S. Route 21 enters South Carolina from Folly Beach area near Charleston Harbor and proceeds through Charleston neighborhoods adjacent to Fort Sumter National Monument, Port of Charleston, The Battery, the Historic District, and corridors serving Charleston International Airport. The highway intersects with Interstate 26, U.S. Route 17, and South Carolina Highway 7 while paralleling rail lines used by CSX Transportation and serving connections to North Charleston and Summerville. Continuing northwest, the route passes near Moultrie County? (note: placeholder) communities and crosses Ashley River, skirting Patriots Point and access to USS Yorktown.
Proceeding into Berkeley County and Dorchester County, U.S. Route 21 links Moncks Corner and communities with access to Lake Moultrie and Santee Cooper. The corridor interchanges with Interstate 95 and converges with U.S. Route 17 Alternate near Summerville and St. George, providing routing toward Columbia and connections to University of South Carolina. Further north, the highway crosses into Colleton County and approaches Walterboro, adjacent to Colleton County Courthouse, Neeses, and historic plantations linked to Rice cultivation heritage and the Gullah cultural region. Near the northern terminus, U.S. Route 21 intersects U.S. 17 Alt. and meets business routes before ending near Yemassee with access toward Beaufort and the Savannah River corridor.
Designated in 1926 as part of the original United States Numbered Highway System, U.S. Route 21 initially provided a major North–South link between the industrial centers of the Midwest and the Atlantic coast, tying into routes toward Cleveland, Columbus, Charlotte, and Greenville. In South Carolina, early alignments followed preexisting auto trails and turnpikes serving plantations, ferry landings, and market towns such as Walterboro and Moncks Corner, reflecting economic patterns tied to Rice cultivation and timber extraction. The construction of Interstate 26 and Interstate 95 during the mid-20th century shifted long-distance traffic away from U.S. 21, prompting realignments and the creation of business loops in Summerville and Walterboro. Military considerations during World War II and subsequent base expansions around Charleston Naval Shipyard and Parris Island influenced capacity upgrades and connector routes. Preservation efforts in the late 20th and early 21st centuries have engaged South Carolina Department of Transportation, local preservation societies, and municipal governments to balance roadway improvements with protection of resources like Fort Moultrie, Hopsewee Plantation, and Lowcountry wetlands.
Major intersections along the South Carolina segment include junctions with federal and state corridors that serve regional and interstate travel: the connection with U.S. 17 near coastal Charleston, the interchange with I-26 providing access toward Columbia, the crossing of I-95 facilitating north–south long-distance routes, and intersections with U.S. 178 and South Carolina Highway 27 serving local mobility. Other significant nodes include links to U.S. 78, U.S. 176, and state highways that provide access to Beaufort County and Hilton Head Island. These interchanges and at-grade junctions form a network connecting to Port Royal, Bluffton, Beaufort city, Charleston County ferry terminals, and military installations such as Marine Corps Recruit Depot Parris Island.
Planned improvements and studies involve projects by the South Carolina Department of Transportation in coordination with county governments and metropolitan planning organizations such as the Charleston Regional Development Alliance and Beaufort County Council. Proposals include corridor widening to improve capacity near Summerville and Moncks Corner, intersection upgrades at nodes interfacing with Interstate 26 and U.S. Route 17, and resilience projects addressing sea level rise impacts from Atlantic Ocean storm surge in Lowcountry marshlands. Federally funded bridge replacements and pavement rehabilitation projects involve programs administered by the Federal Highway Administration and reflect priorities in National Highway System planning and South Carolina Statewide Transportation Improvement Program. Environmental reviews reference resources like ACE Basin National Estuarine Research Reserve and assessments related to Coastal Zone Management Act considerations.
- United States Numbered Highway System - U.S. Route 21 - Interstate 26 in South Carolina - Interstate 95 in South Carolina - U.S. Route 17 in South Carolina - Charleston, South Carolina - Beaufort, South Carolina - Moncks Corner, South Carolina - Walterboro, South Carolina - South Carolina Department of Transportation - Fort Sumter National Monument - Port of Charleston - Santee Cooper - ACE Basin National Estuarine Research Reserve - Marine Corps Recruit Depot Parris Island - Historic District (Charleston)