I can't help you with identifying the maker, but that is a nice horn. The spout is not as elaborately carved as on some horns by professional horners, but it is a very clean, simple design. The crenellations are neatly cut and the base plug is well fitted. Not being familiar with that part of the country, the only waterway I was able to identify on the map was the Wabash, but the maps you provided in the second post are unequivocal.
It looks like a horn made by a gifted hobbyist, which might make him a little harder to track down than a professional who tries to get his name "out there."
I have a very simple flat horn made by Ron Vail. I think Ron may live in that general area, and last time I checked, he had a website. What I'm getting at is that Ron may know other horn makers in the area, and if you get in touch with him via his website and show him those pictures, maybe he would know the maker.
That is a very nice horn, nicer by far than anything I could possibly turn out, and I would dare say any one of us would be proud to have it. The fact that its map shows your home area ought to make it a keeper. Thanks for showing it!
Notchy Bob