The majority of IL 3 has four lanes from Waterloo to Godfrey, with brief six-lane stretches from the entrance to the McKinley Bridge in Venice to near the River's Edge area (formerly the Army Depot) in Granite City and near Alton Square Mall in Alton, as well as a brief two-laned section between its separation from I-55, I-64, and US 40 in East St. Louis and Venice.

It is also two-laned the majority of the southern part from Waterloo to Cairo near areas of the Shawnee National Forest, as well as the northern portion from Godfrey to Grafton.

On August 4, 1976, the new Berm Highway from Wood River to Alton was opened.

[3] It was signed as IL 3, which left the old alignment on Lewis and Clark Boulevard and Broadway unmarked.

On November 26, 1987, a new section of Homer M. Adams Parkway in Alton opened to traffic, and IL 3 was extended onto Lewis and Clark Boulevard (a former IL 3 alignment) back into Alton and onto the extension.