You pretty much have to go to each campgrounds website to find available dates.
Even chain campgrounds like KOA's are independantly owned.
Also, because spots are reserved sometimes months in advance, and then cancelled, it would be impossible to have an up to date database of available sites, or what is or may become available.
Steve & Cheryl + Zoey, and Ziggy, our furry kids.
2012 Forrest River Lexington 283ts
2013 Subaru Crosstrek toad