If you aren't in a big hurry, I strongly suggest you get off the interstate and travel the back roads. Their backroads out there are usually very nice to travel down. That way you get to see all the farms and little towns along the way. A lot of the towns will have places you can park for the night, sometimes even with hookups. If you don't see a place posted, just ask one of the locals or sheriff and they can advise.
Some of the nicest parks and interesting things we found while traveling the back roads.