[4] Established in 1922 as an original state highway, it traversed from the Georgia state line to SC 8 (Guess Street/Green Avenue) in Greenville; connecting McCormick, Abbeville, Due West, Honea Path, Belton, and Williamston.

Also same year, SC 20 was extended back along its old alignment north to a rerouted US 29, just south of Greenville.

In 1962, SC 20 was extended into downtown Greenville, along Grove Avenue, ending at US 25 (Augusta Road), replacing US 29 Business (US 29 Bus.).

In 2000, SC 20 was extended to its current northern terminus at Falls Park Drive (formerly Camperdown Way) just shy of US 123, replacing part of US 25 Bus.

They pass Piedmont Technical College's Abbeville County Campus before intersecting SC 28.

They travel through rural areas of the county, passing a United States Department of Agriculture Service Center, the Pete Smith Sports Complex, and the Abbeville County Industrial Park.

They have an intersection with the eastern terminus of Old Calhoun Falls Road and the western terminus of Haigler Street, the former of which leads to the Abbeville County Law Enforcement Center, the Sheriff's and magistrates's offices, and detention center.