There does not seem to be a check-in or check-out time as of May, 23rd 2023. There is no real order to anything here.

This National Park campground is managed by a concessionaire. Reservations are available through Cedar Pass Lodge. It is best to call the Reservation Phone number, but if I remember correctly there is NO one to "check you in" so as soon (or late) as the site is open you can check in.