Partly depends on what part of the country. Out here in CA, State and National parks are generally 35 ft (actual bumper to hitch). There are some sites that can support bigger but they are limited. Sometimes it is not the length of the driveway, but the tightness of trees and rocks to the road that prevent manuvering. If you make a reservation and do not fit, they may try to find something bigger, but are under no obligation to, and due to the popularity of our State and National parks, there may not be anything else available. It is one of the reasons we have stayed with a small rig. Even then, I sometimes have trouble finding spots because I have to park the tow vehicle somewhere too.
