Interstate 55 begins in Chicago along Lake Shore Drive (US Route 41) and heads southwest along the former route of US Route 66, crossing the Mississippi River into St. Louis, Missouri. It passes along Joliet's western flank and connects to Normal, Bloomington, and Springfield before it reaches the St. Louis metroplex.
Exit 250B loops around to access Interstate 80 west, toward "Iowa":
Exit 251 creates the southern start of Illinois 59 toward Plainfield and Shorewood, but it only connects to Interstate 55 to/from the south:
Exit 253 accesses US Route 52, linking to Joliet and Shorewood:
Exit 257 connects to US Route 30 alongside Plainfield, but signs only point to Aurora and Joliet:
Exit 261 is the eastern end of Illinois 126, marking a curve into an east-northeast alignment that Interstate 55 follows until its very end, and the partial interchange only allows Illinois 126 to/from the east-northeast: