No just get there early and set up thats what i did
Army core of engineers
You can go to recreation.gov You may get lucky if you get there early, but there technically is a fee ($75-135 depending on location) to reserve a pavilion. If someone payed for one for the day, and it wasn't marked off for some reason, I can foresee some ensuing chaos lol.
https://www.recreation.gov/camping/campgrounds/233330/availability
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