The highway was formerly part of U.S. Route 30S (US-30S), prior to being bypassed and replaced with what is now signed as Interstate 84 (I-84).

The highway eventually reaches the ghost town of Cedar Creek, where it turns to the east-southeast.

[3] The road from SR-17 (now SR-82) in Tremonton northwest to Snowville became a state highway in 1912 as part of the Midland Trail (which continued to Nevada via present SR-30.

[4] The state highway was extended to Idaho in 1921,[5] became part of US 30S in 1926,[6] and received the (unsigned) SR-42 designation in 1927.

[5] The American Association of State Highway Officials approved the relocation of US-30S onto I-84 in 1970, after which the first SR-42 signs were placed on the route that had been so designated since 1927.