According to the camp host, the even numbered sites are walk in. Odd are reservable. If you go on a week day you can probably get a walk in with no problems. The weekend can get busy so if you can, make a reservation.
Generally, yes, although they do reserve a few sites for walk-up reservations. Go to recreation.gov to make a reservation.
There are walkin sites that are on a first come basis. I like to reserve so I know I have a good spot.
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