Lemont was on the initial alignment of SBI 4, which followed the Lone Star Route and Pontiac Trail. IL 4 was later moved across the river to the west, and the eastern routing of IL 4 then became IL 4A. Before that happened, US 66 followed the original route from its inception in 1926 to roughly 1927/28, as the western route was not yet completed, with a portion west of Lyons still unpaved. The newer route of IL 4 was straighter and less populated at the time, resulting in the eventual bypass of IL 4A.