SC 18 was established in 1938 as a renumbering of SC 111, from
U.S. Route 29 (US 29) in Gaffney, to the
North Carolina state line. In 1940, SC 18 was extended south along new primary routing to
SC 9 in
Pacolet. In 1942, it was extended again along new primary routing to
SC 56 south of
Glenn Springs. In 1960-1961, SC 18 was rerouted at Gaffney to
US 176/SC 9 in
Jonesville, replacing part of
SC 11; its old alignment became part of
SC 150. In 1989, SC 18 was extended to its current western terminus at US 176/
SC 215, replacing part of US 176 and all of
US 176 Bus.
South Carolina Highway 18 (1922–1938) The first SC 18 was an original state highway, established in 1922 between
SC 20 in
Abbeville northwest to
Anderson and then northwest to
SC 17 in
Westminster. The next year, it was extended north-northeast to
SC 2 in
Walhalla. Two or three years later, its Westminster–Walhalla segment was eliminated, and it was routed from Westminster to the
Georgia state line northwest of
Long Creek. Its former path was redesignated as
SC 183. In 1933, its western terminus was truncated to Westminster, to an intersection with
US 76 and
SC 13. Its former path was redesignated as part of US 76. In 1938, SC 18 was redesignated as part of
SC 28 from Abbeville to Anderson and
SC 24 from Anderson to Westminster.
Antreville alternate route South Carolina Highway 18 Alternate (
SC 18 Alt.) was an
alternate route that existed in
Antreville. It was established in November 1936 between
SC 184 and SC 18 (now
SC 28). In 1938, it was
decommissioned and redesignated as
SC 28 Alt. Today, it is a secondary road. ==Major intersections==