Illinois Route 5 is a four-lane road that runs from U.S. Route 67 in Rock Island to the interchange of Interstate 80 and the toll-free portion of Interstate 88, a distance of 15.78 miles (25.40 km). Illinois Route 92 also continues eastbound on Interstate 88.

Illinois 5 is the main road on the north bank of the Rock River, and serves the cities of Rock Island, Moline, Silvis, and Carbon Cliff.

The entire route is in Rock Island County.

SBI Route 5 originally ran from East Dubuque, Illinois to Chicago, mostly along the current U.S. Route 20. The portion that ran from Belvidere through Rockford became Business Route 20 in 1967.

In 1972, Illinois 5 was applied on the former Illinois Route 190, and what was then the tolled portion of U.S. Route 30. In 1975, Illinois 5 was designated as the East-West Tollway and extended to Rock Island, replacing some of Illinois Route 2 in the process. In 1990, Illinois 5 was changed over to Interstate 88 east of Interstate 80, while the portion of Illinois 5 in the Quad Cities remained.