If you are going to Chicago, Then it stands to reason that you will most likely be driving through or near the Quad Cities. This is on the Illinois Iowa boarder, split by the fabulous Mississippi River. A drive along the Mississippi River is outstanding.
While here, you can go visit the German American Heritage Center, which is located right across the Centennial bridge from Rock Island, Illinois in Davenport, Iowa http://gahc.org/
Notable local cuisine include Maid Rites http://maid-rite.com/ Harris Pizza http://www.harrispizza.com/ for Quad City style pizza, and for desert Whiteys Ice Cream http://www.whiteysicecream.com/
If you want to include that in your stop, let me know.