^A trailblazer as Interstate 255 bends from southerly to westerly at the southern Illinois 3 interchange near Columbia, February 2022.
Interstate 255 forms the southern and eastern portions of a beltway around St. Louis, Missouri, meaning that it spends most of its time in Illinois. Some of Interstate 255 is in Missouri. Interstate 255's northern end is at Interstate 270 northeast of Saint Louis, near Edwardsville, Illinois. From there, Interstate 255 runs southerly and southwesterly, turning near Columbia, Illinois, to head westerly across the Mississippi River into Missouri for its remaining three miles.
Exits 1 to 3 are in Missouri, so this page will start at the first Illinois exit, Exit 6, and continue north to the final exit at Interstate 270.
Interstate 255 crosses into Illinois, with US Route 50 along for the ride, on a bridge across the Mississippi River:
Exit 6 is a directional stack interchange to Illinois 3's southern continuation toward Columbia, Illinois; at this interchange, Illinois 3 joins Interstate 255 north, and Interstate 255 turns northeasterly to flank the eastern side of the Metro-East:
Exit 9 is sort of a half-folded interchange to access the town of Dupo:
Exit 10 is a trumpet interchange that allows Illinois 3 to continue on its own route north toward Cahokia Heights and East St. Louis:
Exit 13 is for Illinois 157 to Cahokia Heights, at a fountain interchange with a bonus loop onramp (from eastbound Illinois 157 to northbound Interstate 255):
Exit 15 is a standard diamond interchange to Mousette Lane:
Exit 17A is the first half of a cloverleaf to Illinois 15; this first ramp leads eastbound toward Belleville:
Exit 17B, the latter ramp in the cloverleaf, leads to Illinois 15 westbound along Missouri Avenue into East St. Louis:
Exit 19 is for State Street into East St. Louis:
Exit 20A is the first half of a cloverleaf to Interstate 64; this first ramp leads eastbound toward Louisville, and it carries US Route 50 with it:
Exit 20B is the ramp to Interstate 64 west toward St. Louis (and it doesn't go much farther than that):
Exit 24 is a half-folded diamond interchange to Collinsville Road: