The Sugar River Trail might be of use.
The Wisconsin DOT has a link for bicycle maps:
Wisconsin used to have the Wisconsin Bikeway, which ran from Kenosha to LaCrosse. I rode it many years ago. I couldn't find a link to it, though.
Iowa has a bicycling link:
Iowa has a famous annual cross-state ride every year, RAGGBRAI, sponsored by the Des Moines Register newspaper. It wouldn't surprise me if they had a ride starting in Dubuque sometime in the past.
You can find rails to trails info here:
I don't know anything about Nebraska.