You only arrive and pay for the entrance
It's first come first serve. However, they have the best campground host that I have ever encountered (Chuck is his name).
You can just show up and camp if there are spots available. It's first come. There is an office that you can stop at before you go into the campground if you need to purchase a park sticker ect. But there are envelopes and drop box by the bathrooms to pay for your campsite.
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