I have stayed at several KOA's. There is no check-in time, its when ever you get there. Check out is 24 hours later, pretty sure. I do love Koa for traveling. They are always nice to very nice, and mostly easy access from the main highways. I have pulled into one at 10:30 pm, long after the office closed. They always have a self serve deal, fill out the envelope, put money in, drop it in the box, go to your site. Then I left at dawn the next morning, I never saw the campground operators.