Originally Posted by
Doug64
Check out Michigan's Trail systems. They have about 2700 miles of trails; some of them meet your criteria. Also look at Idaho's Trail of the Coeur d' Alenes.
Rails to Trails
Yep, the only caveat to the OPs request being is that there are a lot of connectors between the randomly completed trails, it is hard to ride more than a few dozen miles without following some sort of open-to-motor-vehicle traffic.
That said, I still highly recommend them, and can't wait for the day the Airline Railway and the Iron Belle trail are fully complete.