Some touring bicyclists have started a non-commercial website, Bicycle Touring On Car Free Paths, on how to do the great long-distance car-free bike paths in North America -- where the paths are, narratives on their settings in nature and history, information on lodging and camping, restaurants and food, ice cream and beer, bike shops and shuttle services -- basically, what the touring cyclist would want to know to plan a trip that could be across the state or across the continent.
We hope other touring bicyclists will continually add content -- their own suggestions for doing the trips as well as pictures -- to keep it current and expand it out. And as more touring bicyclists write us about their favorite car-free paths not now covered, the list of paths on the website will grow. If more people are on the paths, we might get more and better paths.
Paths covered on the site now include the C&O Canal, the Great Allegheny Trail, Greenbrier River Trail, Mickelson Trail, Silver Comet/Chief Ladiga, P'tit Train du North, Kettle Valley Trail, the Coeur d'Alenes, and the Katy Trail.
At this point, some paths are covered in more detail than others, a shortcoming we hope updates from touring cyclists will correct.
Much appreciate advice from touring cyclists who've ridden the Coeur d"Alenes, P'tit Train du Nord, Silver Comet/Chief Ladiga, and Kettle Valley Railway trails, on lodging (motels and camping), food ice cream and beer, and services. Pictures needed too! Thanks, Jeff at http://bicycletouringoncarfreepaths.org/
MN also has a lot of off road trail miles that are open to bikes, but their system doesn't link up to WI's very neatly. IL's got the Great Illinois trail system, tho it is not all off road.
If you're serious about this project, I'd really recommend doing more research with various states' transportation departments and the fish and game or wildlife or department of natural resources. Here in WI, I know they want to link up Glacial Drumlin to Milwaukee's trail system and to Madison's. A lot of the Ice Age trail isn't finished yet, and it will eventually provide links between the northern trail systems and the southern.