U.S. 21 originates at Hunting Island State Park along the Atlantic coast in South Carolina. The route leaves the Palmetto State alongside Interstate 77 from near Carowinds theme park into Charlotte, North Carolina.
U.S. 21 South Carolina Guides
U.S. 21 connects Beaufort and coastal areas of the LowCountry with U.S. 17 near Pocotaligo and I-95 north of Yemassee. The rural highway continues northward to Smokes in Colleton County and Branchville in Orangeburg County.
North from Rowesville, U.S. 21 reaches the city of Orangeburg. U.S. 21 bypasses the Orangeburg County seat with U.S. 601 Truck and U.S. 178 while U.S. 21 Business stays to the west near the city center along a 2.73 mile long course. U.S. 21 resumes along a rural route northward to Calhoun County and I-26 in southeastern Lexington County.
U.S. 176 converges with U.S. 21 near the settlement of Sandy Run. The two routes overlap for 30.72 miles north to Cayce and Columbia. U.S. 321 joins U.S. 21/176 from near Dixiana to Belleview in the capital city. U.S. 76 joins the three routes on Elmwood Avenue four blocks east from Interstate 126 to Main Street as well. Prior to 1977, U.S. 21/176/321 followed Blossom Street (U.S. 21 Connector) east and Assembly Street (S.C. 48) north to U.S. 76 at Elmwood Avenue with the alignment along Huger Street posted as a truck route. An application to reroute U.S. 21/176/321 over the truck route was approved by the American Association of State Highway and Transportation Officials (AASHTO) on October 29, 1977.
U.S. 21 accompanies the I-77 corridor north from Columbia to the town of Blythewood. Shifting to the east of I-77, U.S. 21 enters Fairfield County ahead of Ridgeway. Through Chester County, U.S. 21 connects the towns of Great Falls and Fort Lawn.
Within York County, U.S. 21 transitions into a four lane highway leading into Rock Hill. Looping west of I-77, U.S. 21 combines with S.C. 121 along an arterial route bypassing the city to the east. A business route for U.S. 21 previously looped 6.78 miles west to Downtown Rock Hill along a combination of S.C. 5/121 (Main Street E), Black Street, Oakland Avenue and Cherry Road. The city of Rock Hill requested to take over maintenance for part of U.S. 21 Business from the South Carolina Department of Transportation (SCDOT) to gain full oversight for future economic development projects at Downtown. Since the transfer resulted in separate segments, U.S. 21 Business was decommissioned with concurrence by the American Association of State Highway and Transportation Officials (AASHTO) on May 3, 2013.
U.S. 21 angles northeast across I-77 again from Rock Hill toward Fort Mill, where a 7.06 mile long business route branches to the east. The two routes converge south of S.C. 51, the old route of U.S. 21 to Pineville, North Carolina.
North
A diamond interchange with a roundabout joins U.S. 21 (Trask Parkway) north with U.S. 17 (Charleston Highway) at Gardens Corner.
12/31/17
Northbound U.S. 21 partitions into single lane ramps for U.S. 17 north to Charleston and the 6.38 mile long overlap with U.S. 17 south toward Savannah, Georgia.
12/31/17
North 
West
S.C. 6 overlaps with U.S. 21 north en route to Swansea.
09/16/21
S.C. 6 accompanies U.S. 21 (Columbia Road) north 1.57 miles to Center Hill Road.
09/16/21
S.C. 6 continues 10.8 miles west to U.S. 321 in the town of Swansea.
09/16/21
North
Sunny Plain Road (Road 30) ties into U.S. 21 at the north split with S.C. 6 ahead of this confirming marker.
09/16/21
U.S. 21 north descends to Big Beaver Creek and the Lexington County line.
09/16/21
09/16/21
S.C. 322 (Cherry Street) heads northeast along the former route of U.S. 21 Business to U.S. 21 (Anderson Road) on the north side of Rock Hill.
09/20/21
South
U.S. 21 (Trask Parkway) south of the roundabout interchange with U.S. 17 (Charleston Highway).
12/31/17
Connect with:
Interstate 20
Interstate 26
Interstate 77
Interstate 95
Interstate 126
U.S. 1
U.S. 17
U.S. 17 Alternate
U.S. 76
U.S. 78
U.S. 176
U.S. 178
U.S. 301
U.S. 321
U.S. 378
U.S. 601
Highway 6
Highway 63
Highway 64
Highway 217
Page Updated 03-14-2022.