Sorry forgot to tell you that it is near the stillwater mine outside of Lewistown, pretty close to where you are. I would also reccomend that you go to a sporting goods store that sells fishing stuff, they usually have good topo maps for like 5 bucks, pick one up pack your ruck and let the adventure begin. You would't believe how much fun it is to try navigating through the unknow mountains of Montana with only a topo and a compass. Just be sure to bring some extras incase you get weathered in. One more really fun place is the prior mountains near Bridger, make sure you pack a gun up there though don't want to surprise any bears without some way to stop em.