We just left Yellowstone. I don't know how it is possible to cover anything other than a very small fraction of the park in one day, at most of that will be a drive by. Aside from the distances that need to be covered, the park is enormous, traffic will keep you at a crawl for long periods of time. Any wildlife visible from the road will result in a long and lengthy traffic jam. You won't cover a lot of miles in a short period. Having said that, it appears that every RV campground inside the park has a "Full" sign out front. Chuck