US 25 ALT #1: Appeared as early as 1932 as a renumbering of US 25 from Greenville in a loop west back around to US 25 near Travelers Rest.
In 1947, US 25 ALT was downgraded to S-23-13. Today it is a little SC 183 Pete Hollis Blvd; S-23-1080 Buncombe Rd, and S-23-13 Old Buncombe Rd.
US 25 ALT #2: Appeared Sept 1936 (SCDOT) as new BELT routing from US 25/SC 23 Edgefield south a mile, then east back to US 25.
Between 1952-54, US 25 ALT was downgraded to S-19-10 on Hauskett St and S-19-22 on Penn St (now S-19-34). The Hauskett Ave portion is now US 25 TRUCK.

US 25 ALT parallel and west of US 25-276 1940 Greenville County

US 25 ALT in Edgefield 1940 Edgefield County

US 25 ALT #3: Appeared by 1940, connecting US 178 to US 25-178 in Hodges.
By 1945, US 25 ALT became SC 185. This routing would've made way more sense as US 178 ALT and I wonder if the 25 ALT and 178 ALT designations on the 1940 Greenwood County map are backwards.

US 25 ALT into Hodges 1940 Greenwood County

SC 185 replaces US 25 ALT 1945 Greenwood County