Illinois 13 has its western terminus at Cahokia Heights at Illinois Route 157 and its eastern terminus at the Kentucky state line and the Ohio River, at Kentucky Route 56.

Continuing southeast, IL 13 largely serves Belleville's business district, unlike the expressway.

Both routes then turn south towards Freeburg along a four-lane divided highway.

At the village limit of Freeburg, the road downgrades into a four-lane undivided highway.

Continuing south, IL 13 turns eastward, leaving the concurrency.

It then crosses the Big Muddy River as a four-lane divided highway.

It then intersects IL 148 southwest of the Veterans Airport of Southern Illinois.

One of its first governmental tasks was the construction of primitive dirt roads between the three pioneer villages of Cahokia, Kaskaskia, and Shawneetown.

Illinois Route 13 did not take its current physical form, though, until after the enactment of the Good Roads Movement paving program in 1918.

The statewide plan standardized the alignment of this road and numbered it Illinois 13.

[4][5][6] Another reroute took place between 1944 and 1947 when Illinois 13 took over a new highway (then called U.S. Route 460) in and around Belleville.

[3] To address congestion in downtown Harrisburg, the Illinois Department of Transportation undertook a project to build the Bill Franks Bypass, a new four-lane road to reroute IL 13 around the city center.