Debbie KC9ULA and me, KO0Z checked out a promising tower site about 5 miles southwest of Mason City, IL EN50ce. For reference Mason City is about half-way between Springfield, IL an Peoria, IL. It is a high location, but there is a stand of trees that could be a problem pointing north. The east location looks promising and depending on corn, a path to St. Louis is possible. It's not the greatest site, but it does offer some possibilities. Ron W9ZIH in EN51nv is 127 miles away, Zack in EN50rl is 69 miles away and St. Louis is about 110 miles away.
Mason City, IL Tower site EN50ce. Looking west on County road 850N
EN50ce Tower
Looking north from EN50ce
Looking northeast and east from EN50ce
Debbie KC9ULA and southeast in the background