If you wanted to go up to Minneapolis, there is a pretty good trail section that you could incorporate into your route, start with the Jane Adams trail (google it for more info) which connects with the Badger State trail in WI and takes you up to Madison. From there you could revert back to roads (Dane and Sauk counties, see county maps) until you connect to the four trails route (one of the links below) to get to the Mississippi. Then take the Great River Road up north a ways.
I am unaware of a good route map that would string all of this together but I think a lot of it could be done with very little research.
Some useful links:
Bicycle trails - Wisconsin DNR
Wisconsin Department of Transportation Great River Road (Mississippi River Trail) Bicycle Map
Wisconsin Department of Transportation Travel by bike
http://www.bike4trails.com/Bike4Trailsmap.pdf
Wisconsin Department of Transportation County bicycle maps
May or may not help.
State Trails Map: Minnesota DNR
If you wanted to add a train ride from St Paul MN to Chicago at the end, the Empire Builder train could take you home. The timetable for a ride however might not be the most convenient.
Wisconsin bike trails require a trail pass, annual price is up to $25 now.
Minnesota DOT also publishes a state highway map oriented towards bicycling, I have a paper copy but do not know how to ask them for a copy. Maybe google would help.