We discovered over the past two summers that truck stops are most easily found along interstate highways...perhaps this has been your experience, too. Hubby and I found that to be a distinct disadvantage to the US and state highways...plus the lack of rest areas! Wal-Mart and Target started to take the place of truck stops as we traveled, for restrooms. (Some of those, as you may know, allow RV's or camper vans to stay overnight for a certain period of time. Some don't, like our local Wal-Mart, because of local ordinances. They made an exception during the fires of 2003 and 2007.)
I'll second Mark's vote for I-70 between Cove Fort and Green River, UT, being especially scenic. We also love I-70 between Grand Junction and Denver, CO, for spectacular scenery. It's one interstate that we never get tired of! I-8 between Alpine CA and Jacumba, CA is also quite pretty, but in a totally different way. Others may laugh at me, but I found I-40 in Arkansas and Tennessee to be beautiful -- love the forests!
Donna
Donna