[1] Illinois 109 is a two-lane, undivided surface road in Jersey County for its entire length.

Traveling northbound from IL 3, it goes directly north for a short distance, and then curves.

Right after these curves, it passes by unincorporated McClusky, and resumes traveling due north for the remainder of its length.

Within the town of Jerseyville, it picks up the name McClusky Road.

Its northern terminus is at US 67 (State Street) in Jerseyville.