Utah State Route 126

After its southern terminus, the route heads northwest in Layton. After entering Clearfield, the route turns straight to the north. It continues this direction through Sunset, Roy, and West Haven before veering to the northwest when the highway reaches Marriott-Slaterville. The route again reverts to a northerly direction before reaching Farr West. Just before terminating in South Willard, the route turns northeast one final time.

The entirety of the route, with the exception of a small portion from the Interstate 15/Interstate 84 junction to the northern terminus, lies west of the aforementioned interstates.

The portion of what is now numbered SR-126 from the southern terminus to the junction with SR-26 was previously part of US-91.[3] The northern portion of what is now SR-126 was numbered State Route 84 starting in 1953.[4] In 1974, US-91 was eliminated throughout most of Utah,[5] and SR-84 absorbed the portion of former US-91 from Layton to Roy.[4]

The 1977 Utah state route renumbering was implemented, in part, to eliminate instances where a state route used the same number as a U.S. Route or Interstate route in the state. As the 84 designation was also in use for Interstate 84 most of SR-84 was renumbered to SR-126.[4] The only change from then to now was a portion of the old highway that was relinquished to be used by the city of Layton for parking lots in 1991.[2]