Yes. But if you come in late with no reservation, you can pick a spot that doesn't have a card on the post or a camper. Then in morning go to office and pay for site.
No you do not need a reservation. You can just show up at the office and if they have a spot open you can get it. Weekend's are usually full but during the week it isn't that busy. They have one walk in tent site that is pretty awesome.
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