Traversing a total of 3.68 miles (5.92 km), it starts at exit 108 along I-26, it has exits with Colonial Life Boulevard (westbound only) and Greystone Boulevard (to Riverbanks Zoo), before crossing the Broad River on the Timmerman Bridge. Entering downtown Columbia, it merges briefly with US 21/US 176/US 321, at Huger Street, before ending at Gadsden Street. It is named the Lester Bates Freeway and is co-signed with US 76 for the entire route.
I-126 started construction in 1959 and was completed in 1961 as a four-lane freeway. Relatively unchanged since inception, it was widened to six-lanes in the 1990s and its eastern terminus has fluctuated between Huger Street and Gadsden Street.
Interstate 126 Business (I-126 Bus) was a boulevard-grade business spur of I-126 along Elmwood Avenue, between Huger Street and Main Street; in concurrence with US 21/US 76/US 176/US 321. Signage appeared in the 1980s, by 2000 all but one sign remained on the route. At some point[when?], I-126 absorbed part of the business spur from Huger Street to Gadsden Street. It is considered decommissioned as no current state/federal maps list it, nor any physical signage exists.