The key is to book a year in advance. I'm thinking about booking for 2022 but when I book I thinking about booking before school is out in May or after Labor Day.I'm not sure why the NPS is so opposed to some type of lottery system. Yosemite, Zion, and Yellowstone are absolute zoos. I know they are "our" parks, but it is crazy. I am happy people are interested, but there seems to be an expectation of convenience.