I recommend reservations. You might be able to technically manage by winging it, but if you have any care at all about what quality of site you get, then definitely, definitely, definitely make reservations. The sites that are apt to be available short notice are what are-imho— the shitty sites: ones that are right on top of the bathroom ( you don’t wanna be way far away, but being right close to it is an ick) or the blahh sites that are out in a field with no pretty forest surroundings.