Interstate 20 (I-20) is the main east–west Interstate Highway in the state of South Carolina, linking the state with important transportation and business hubs to the north, west, and south, including Atlanta, Georgia; Charlotte, North Carolina (via I-77); Savannah, Georgia (via I-95); and Washington, D.C. (via I-95).

I-20 travels 141.51 miles (227.74 km) west to east, from the Georgia state line at North Augusta, through Columbia, to end at I-95 in Florence.

Known as the J. Strom Thurmond Freeway (named for the US senator), the highway heads northeastward, bypassing Aiken and Lexington before reaching the state capital of Columbia.

It was constructed in various stages beginning in late 1963, with the final section between South Carolina Highway 340 (SC 340) and I-20 Bus.

At Columbia, I-20 crosses the Saluda and Broad rivers and travels through the northern part of the city and turns eastward, bypassing Fort Jackson and Camden before reaching Florence.

The South Carolina Department of Public Safety and State Transport Police operate and maintain two truck inspection/weigh stations.

In 2005, this proposal became part of the SAFETEA-LU transportation legislation, and North Carolina received $5 million for a feasibility study for this extension.

If built, I-20 will have a concurrency with I-95 about 12 miles (19 km) through Florence, meet I-73 near Marion, have concurrency with a I-74 about 20 miles (32 km) from Whiteville to east of its future interchange with North Carolina Highway 211 (NC 211), and have future interchanges with I-140/US 17/US 74 east/US 421/NC 133 in Wilmington where I-20 will terminate at bridge crossing over the Cape Fear River where US 17/US 76/US 421/NC 133 crosses into downtown.

In 2009, soon after Governor Mike Easley left office, the proposed routing was removed from all NCDOT plans and was officially dropped.

[11] SCDOT, in cooperation with the FHWA, is proposing improvements to a corridor along I-20, I-26, and I-126, including the system interchanges at I-20/I-26 and I-26/I-126 in Lexington and Richland counties.

The project will widen 1.8 miles (2.9 km) of I-20, replace four bridges over the Augusta Canal and Savannah River, and make intersection improvements at the West Martintown Road interchange in South Carolina.

appears past West Evans Street indicating the route continues to its official eastern terminus at an intersection of US 76.