At Lilac, I-270 constricts to four lanes as it crosses the Mississippi River on the New Chain of Rocks Bridges. Approaching Missouri and entering Illinois, I-270 transitions from a suburban Interstate to an exurban Interstate with farm fields and wooded land bordering the Interstate in the area to the immediately east and west of the river crossing. Once it crosses the Chain of Rocks Canal, I-270 will intersect four different highways providing access to communities in eastern Madison County: IL 3, Old Alton Road, IL 203 and IL 111. The interchange with IL 3 is a partial cloverleaf with the loop ramps in the northeast and southeast quadrants. The remaining two are cloverleaf interchanges, with the Old Alton Road/IL 203 interchange using a collector–distributor system with two folded diamonds due to the presence of railroad tracks between the two roadways. Once it passes IL 111, the speed limit increases to as the highway briefly becomes six lanes again with the junction with I-255. The highway then reverts to a four-lane highway offering diamond interchanges with IL 157 and IL 159 before meeting up with I-55/I-70 at the interchange that IDOT refers as the "3 I's". The eastbound I-270 meets the northeastbound combination of I-55 and I-70 which leave the intersection as northbound I-55 and eastbound I-70 which has adopted I-270's mile markings.