Intersections from west to east:

US40 enters Illinois crossing the Poplar Street Bridge over the Mississippi River at St. Louis, along with Interstates I-55, I-64, and I-70

IL3 joins from the south at East St. Louis. (While IL3 is multiplexed, there are five routes all following the same highway.)

I-64 splits off to the east, as IL3 splits off to the north at East St. Louis

IL111 near Washington Park

IL157 near Collinsville

IL159 near Collinsville

US40 breaks off of I-55 and I-70 near Troy

IL162 near Troy

IL143 joins from the west at Highland

IL160 joins from the north at Highland

IL160 leaves to the south at Highland

IL143 splits off toward the east near Pierron

US40 joins I-70 east into Bond County

It passes through these towns: East St. Louis, Collinsville, Maryville, Troy, and Highland.