In 1924, SBI Route 164 was originally the route from Pekin to west of Bloomington, now part of
Illinois Route 9. In 1937, IL 164 was assigned to the road that had been IL 94A from Monmouth to Gladstone. This route still exists today in Warren and Henderson Counties. The route was extended in the late 1990s along the old U.S. 34 alignment between Monmouth and Galesburg, after completion of the 4-lane freeway upgrade of US 34 in this section. The current eastern terminus is U.S. 150 at corner of Henderson and Main Streets in Galesburg. This was the historic northern terminus of
IL 41. == Major intersections ==