Yellowstone in early August?

Last year we dry camped 4th of july week in Yellowstone and had our pick of sites and campgrounds. Literally none of the non-reservables were full. If all else fails you can always pop outside the park to a private or forest service campground. If you aren't aware already this is your Best resource for all cgs in and around Yellowstone

Side note... if all sites are full you can take a handicap site for one night but must share it should a handicap vehicle arrive later.