It is also used by the Illinois Department of Transportation (IDOT) as a part of Federal-Aid Primary Highway 315 (FAP315) to refer to a future project connecting the cities of Quincy and Peoria via underserved Macomb.

For almost its entire length, IL 336 is a four-lane divided expressway without property access, but has many at-grade intersections with sideroads.

The two highways are concurrent to the point west of BNSF Railway overpass, where US 136 splits off to its former alignment through Tennessee and Colchester.

[2] The Quincy inspired highway was vigorously opposed by State Representative Bill Edley, (D-Macomb).

“Our region has been called “Forgottonia” because we don’t have modern highway connections to major markets, such as St. Louis, Peoria, and Quad-Cities.

Connecting two small communities within our region only maintains our isolation.”[citation needed] Earlier, Edley had been successful in funding the $100M Quad-City US67 four-lane link from Monmouth to Macomb.

Illinois Democrats lost their House majority in the 1994 GOP landslide election, and Edley was defeated as well.

[citation needed] Twenty-two years later neither the Corridor US 67 to St. Louis, or access to the Peoria and Chicago markets have been built or funded.

As a result of this change, IL 336 from Fall Creek at the current junction with I-72, north to US 24 near Fowler, was renamed from I-72/IL 336 to simply I-172.

[9] IDOT launched a series of studies to help facilitate access to west central Illinois, colloquially named Forgottonia for the lack of highways through the region.

The Peoria-to-Macomb study involves an eastern link from Macomb to the Peoria area alongside existing US 136.