SC 43: Appeared in 1923 as new primary routing running from SC 10 (now US 221) McCormick east to SC 21 (now S-19-36) northwest of Edgefield.
In 1925 or 1926, SC 43 east was truncated to a relocated SC 21 (now US 25) west of Pleasant Lane. The old route southeast toward Edgefield became part of SC 21 (now US 25).
By 1926, SC 43 was extended west replacing a bit of SC 10 to end at SC 20 (now S-33-11).
About 1929, SC 43 was extended east as new primary routing to end at SC 19-24-392 (now US 178/SC 39-121) Saluda.

SC 43 original routing 1924 Blue book

SC 43 truncated to relocated SC 21 1926 Official

SC 43 extended to Saluda 1930 Official

In 1933, SC 43 was extended west 5 miles as new primary routing towards the Georgia State Line.
In May 1933 (SCDOT), SC 43 was extended west as more new primary routing to the ferry to Georgia.
In July 1936 (SCDOT), SC 43 was extended from Saluda to SC 391.
Also in July 1936 (SCDOT), a separate piece of SC 43 was created from the Saluda/Lexington line east 8 miles.
In April 1937 (SCDOT), the piece between SC 391 and Lexington County was placed into the state highway system.
In June 1937 (SCDOT), SC 43 was extended east as new primary routing to US 1 Lexington.
In 1939, SC 43 was extended with US 1 into Lexington, then north with SC 6, then east as new primary routing to end at US 1-21/SC 2-5-215 West Columbia.

SC 43 extended to Lexington 1937 Official

SC 43 extended to Georgia ferry 1939 Official

In 1940, SC 43 was given a bridge to connect to GA 70.

SC 43 extended toward Georgia 1933 Official

SC 43 extended to Georgia ferry 1935 Official

SC 43 bridge to Georgia 1940 Official

In 1940, SC 43 was moved to new primary routing bypassing Lexington. Also in 1940, SC 43 was put on new alignment across northwestern Lexington County, leaving behind what is now Jimmie Long Rd and S-32-46 Ridge Rd; S-32-115 Spool Wheel Rd/S-32-114 Peachland Rd-Sim Johnson Rd-Walter Rawl Rd-Hook Land Ln/S-32-215 St Johns Church Rd.

SC 43 original Lexington County routing
1938 Lexington County

SC 43 straightened out plus given a bypass of Lexington
1940 Lexington County

SC 43 replaced by US 378
1952 Official