Intersections from west to east:

IL128 joins from the north at the Fayette/Effingham County line

IL128 leaves to the south at Altamont

IL32 ends as IL33 joins from the west at Effingham

US45 joins from the south at Effingham for a block

US45 splits to head north again in Effingham

IL33 breaks off to head east again

IL130 at Greenup, a fraction of a mile south of the eastern end of IL121

IL49 at Casey

IL1 at Marshall

US40 joins I-70 east

US40 and I-70 continue together into Indiana

It passes through these towns: Altamont, Kemptown, Funkhouser, Effingham, Teutopolis, Montrose, Jewett, Greenup, Martinsville, Casey, and Marshall.