The Michelson trail in South Dakota is a great long one day ride. About 112 miles one way. I suggest taking it in one day (it's about 10-12 hours for a rider in decent shape). I also suggest starting in Edgemont, SD and going toward Deadwood, SD. There are plenty of restaurants, hotels, and casinos in Deadwood.

There is also a 3 day tour event that is held once a year for a fee.