If you are in the midwest like us, don't fret. There are plenty of great places to wheel your pride and joy.
The Badlands is probably the most famous of the midwestern ORPs. It is located in Attica Indiana, just inside the western border. They have a great set of trails from beginer to advanced. They even hold professional events there.
Rockport Illinois also has a large ORP. I have not been there yet, but they offer over 700 acres of open terrain. We hope to make the trek this year.
The Chicago area does offer some trails, but most of these are club only places. I know that Wisconsin has a lot of trails on public land. I'm not sure which are open to trucks and which are ATV only. St. Joseph State Park in Missouri is said to have some facilities. Although I've been told it's more for sand rails. Of course, you can always find creek like we do. Our treks up and down our little home creek have been just as challenging as any at the Badlands. Just make sure you don't make people who live on the creek mad. (wink, wink)