The park rangers gate closes at 10pm. Its not really a check-in. First come first serve unless the site you want is reserved the same time you are there. You can still go into the campgrounds after hours. Just pay your fees in the morning. The rangers or site hosts are not gonna stop paying campers who show up late.
Everyone is right you can go in anytime.
24 hours. After 8pm usually it's self check in. Next day you must actually go to main gate and check in.
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