The route begins at the intersection of 400 North (SR-147) and Childs Road in Spanish Fork, SR-51 heading northeast as a two-lane undivided highway on the latter.

As the road exits Spanish Fork, it heads into a rural portion of Utah County.

[2] The road from Spanish Fork to Springville (leaving the latter on 800 North) was added to the state highway system in 1910,[3] and in the 1920s it became part of SR-1 (US-91).

[4] In 1964, when SR-1 was moved to the newly completed I-15 in the area, the old route between Spanish Fork and Springville became an extension of SR-156 (which had been created in 1962 as a short connection between old and new SR-1 at exit 257).

This split SR-156 in two (with the original section, serving as a spur since 1964, becoming part of the mainline), and the portion on Childs Road and to Springville became a new State Route 51.