45 feet is allowed in all states. The commercial motor coach I used to drive was a 45 foot and it was allowed everywhere. Maybe you meant state parks? The thing you need to watch is wheel base, a camper in the park that I am hosting at right now came in this last week and cut a corner too short and hung up on some large boulders, destroyed 3 compartment doors and the surround fiberglass around his rear tire. The coach was on it's first trip out brand new. He had traded in an older motorhome that was only 5 feet shorter but a lot shorter wheel base so it turned around in a lot smaller space.