The route serves as an east–west connector in the city of Layton in Davis County.

SR-109 begins at the intersection of SR-126 (Main Street) and Gentile Street in the historic section of Layton, close to the historic Utah Central Railroad and the current-day Union Pacific Railroad, and the Layton Frontrunner station.

Shortly after Fairfield, the route splits off from Gentile Street, becoming Oak Hills Drive as it continues east-northeast, climbing into the foothills of the Wasatch Mountains, where it ends at a diamond interchange with US 89.

[2] SR-109 was originally established in 1931 as the road from SR-1 (US 91) westerly for four miles along what is now Gentile Street in Layton.

In 2021, the at-grade intersection with US 89 at SR-109's eastern terminus was replaced with a grade-separated diamond interchange as part of a major project to reconstruct US 89 as a six-lane freeway between I-15 in Farmington and I-84 in Uintah.