Hi bjr2000: We recently moved away from Minnesota or I'd sign up. I'm a former Delano resident now living in Colorado. I got interested in ATVs just recently here in Colorado. I know the local Delano snowmobile club has a trail route along the Crow River and county 16. Of course, riding on the snow is less harmful to the terrain than slashing ATVs would be.
However, I understand Minnesota now has limited use of secondary roads for ATVs. My friend in Watertown was riding his Can Am side by side around town all the time before I moved away. I do not know the "rules", but something like getting a permit from the local police and maybe some street legal equipment like mirrors and signals and the like.
Then the gravel road system would be great riding on ATVs. Who needs trails when we have perfectly good dirt roads that go around lovely lakes or along the rivers in Minnesota. No speeding or stunt riding though.