At the time of the demise, Fran Bogner in Beaver Dam, WI and Rodger Menn in Taylorville, IL were the territory reps for Steiger.  I worked for them from '86 to '88. 

I rode in the very first Steiger with an Allison Automatic at Terry Warner's in NE IL (Warner Impl. in Kewanee?) in the late 70's.
Steven's Impl in Litchfield was a dealer.
George Dunn in Farmer City and Clinton, Tim Rieser was the manager in Clinton.  They were IH.
Like others have said, Walker Schork in Rochelle, Dave White Implement. 
There were others, I think Galesburg?  Around Effingham?  Around Arthur?  Those are the ones I remember.  I'd have to study the map a bit for it to come back!