SR 121 was assigned in 1976 and removed from the primary state highway system in 2021, with the entire length of the route being redesignated as Frontage Road FRCH08.

The highway left the Recreation Area and continued its way to the community of Dixie Valley.

The route continued northward for about 20 miles (32 km) and intersected with Settlement Road in Dixie Valley, where the state designation ended.

[3] After many years of minimal use, NDOT removed the asphalt surface and replaced it with gravel in 2021.

[4] It was removed from the primary state highway system by January 2022.