[1] Illinois 158 is an important east–west highway in the southeastern portions of the metropolitan St. Louis, Missouri area.

It runs from Columbia through Millstadt, Belleville, and near the Scott Air Force Base.

IDOT has used "North" and "South" cardinal direction banners for IL 158 for that concurrency in an attempt to remove confusion in that area.

[2] The Illinois Department of Transportation has included a large portion of Illinois 158 in their Gateway Connector project; a southeastern beltway that would run from Columbia east to Scott Air Force Base, and north to Troy.

At least one organization, the Stop 158 group, has formed to block construction of the road and refocus use of taxpayer's dollars on a new Mississippi River bridge south of St.