One halfway point between Decatur, IN and Yorkville, IL is Toto, IN.
Anadarko, OK ... just west-ish of Oklahoma City, OK
Sideview, TN is your halfway point.
Woodridge, IL
Waukesha, Wisconsin is the halfway point between Madison, WI and Gurnee, IL.
The halfway point from Fort Wayne, IN to Joliet, IL is Knox, IL.
Pierson, IL
Liberal Kansas is close to the halfway point.
The halfway point is just about Mishawaka, Indiana.
Greer, IL.
The halfway point is Eminence, KY.
Chillicothe, MO is the halfway point between Quincy, IL and Topeka, KS.
Morton, IL