I live in the midwest as well and I've never stumbled upon any ditchweed whatsoever. I have some good friends who recently moved to southern Illinois and they've mentioned seeing some 'wild hemp plants' along several different train tracks.

Honestly though man, it's really not worth your time. It's just not going to get you high. I mean, unless you find some real, 100% female buds, you're probably not going to get anything more than a buzz. If that. Who knows though. You can always give it a try. The real trouble is finding the shit...