We've been to Yellowstone NP many times and always go in early September or mid. It's just the best time for us at work. We got in to Bridge Bay once and at that time of year, they block off a portion of the CG leaving just a portion of it open. It's a huge CG, so not sure why they do that. All other CG's there are much smaller, but are full daily. Often, we've stayed outside the park in order to get a site that fits our FW.
2011 Bighorn 3055RL, 2011 F350 DRW 6.7L 4x4 Diesel Lariat and Hensley TrailerSaver BD3, 1992 Jeep ZJ and 1978 Coleman Concord Pop-Up for remote camping
Dave & Renee plus (Champ, Molly, Paris, Missy, and Maggie in spirit), Mica, Mabel, and Melton