IL 255 starts at I-270 in Pontoon Beach and ends at U.S. Route 67 (US 67) in Godfrey, at a total length of approximately 23.3 miles (37.5 km).

The final segment—4.3 miles (6.9 km) from Seminary Road to US 67 in Godfrey, just north of the intersection of US 67 and Montclaire Avenue (IL 267/IL 111)—was opened on November 23, 2012.

Although IL 255 was designed to federal Interstate Highway standards, it was built by the Illinois Department of Transportation (IDOT) using state-provided funds.

Although it was part of the much larger Corridor 413 plan,[3] the local politicians focused mostly on the segment from I-270 to what was then IL 267 north of the Godfrey "Y" intersection.

In 1975, a six-month detour related with the closing of the Old Clark Bridge exposed the need for the Alton Bypass along with the other three routes.