http://www.nps.gov/yell/planyourvisit/backcountryhiking.htmThere is some back country trails / camping. We used to drive from Idaho to the Beckler ranger station and hike in. No roads past the Ranger station. We always called it the SW entrance. We backpacked in several times and also rode horses in several times. Pretty wild country. Good trout fishing. Lots of bear sign although we never ran into one, although we had close encounters with moose with calves several times. There is a CG showing on the map of Yellowstone near Beckler which appears to be in Idaho not the park ( may be a NF CG ). Have no idea how close you could get with an RV or road conditions today. It has been a long time and we were always traveling in a 4WD truck and backpacking not in an RV. Lots of good times but I was much younger then. Be prepared for anything including a lot of big mosquitoes.