We didn't have reservations when we camped and we went in June. We mostly stayed at KOA campgrounds, they were all nice. Hope you find a way to go, you will never regret it. It was one of the places my husband always wanted to go....now mind ya, I have NO desire to go back out there. We left Missouri and went the south route and came back the north route, loved the north route but I am not a dry, not grass, not trees drab person and that is just me.