There should definitely be a few spots open. We went last week and the place was less than half full.
We rolled in around 9 PM on July 4th and still had a few sites available. I believe you have high chances for getting a site on Wednesday
I was up there last weekend. We didn't roll in until Saturday afternoon and it was pretty full but there was probably about 5 sites open. It was pretty full by Saturday evening though. It cleared out a lot Monday so I think you'd have a good chance on Wednesday.
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