Many National Park Campground campsites max out around 25-30 feet in length. However, you will be delighted to learn that there are over 20 national park campgrounds with some big-rig-friendly sites. For example, Grand Canyon National Park’s Trailer Village Campground has pull-through lots that can accommodate an RV up to 50 feet in length. But research and reserve your stay well in advance because campgrounds that allow long RVs book to capacity quickly.