This road, designated State Route 12 proceeded southerly from U.S. Route 91 (US 91) (now I-15) through Logandale and Overton and southeasterly to the former town of St. Thomas a total distance of  and then easterly crossing the Virgin River towards the Arizona state line over a distance of . The portion between US 91 and Logandale was paved by 1935, with pavement reaching Overton the next year.
This road, designated State Route 12, moved southward from U.S. Route 91 (US 91) (now I-15), through Logandale and Overton, then southeastward to the former town of St. Thomas, a total distance of , and finally eastward crossing the Virgin River towards the Arizona state line over a distance of . The section between US 91 and Logandale was paved by 1935, with pavement reaching Overton the following year.