The road from Sunnyside south to Columbia was designated as SR-124 in 1931, and renumbered to SR-123 in 1933. In 1935, the portion from Sunnyside to Columbia was split off and designated as SR-124, which was extended south to Horse Canyon Mine in 1945. Since then, only minorlegal description changes have occurred such as reversing the described direction from southerly to northerly, and replacing "via Columbia" with "through Columbia Junction" after the town of Columbia became part of newly incorporated East Carbon.