For getting from LaPorte County through to other side of Chicago you
might want to check out
http://www.cc4cc.org/ (click "updates" on the
left side of the screen to find routes in gps or "google earth"
format). Also I believe all of the adventure cycling maps can be
downloaded in GPS format through the adventure cycling web site. I
have an idea that if you were to plan a route paralleling I-90 west of
Minneapolis it may be fairly easy find low traffic roads as I think
I-90 would draw most of the traffic.
-Jim Moffitt