Yes that 45th parallel sign is inbetween Gardiner MT and Mammoth Hot Springs I worked for years for the NPS and my guess is if we contacted them and told them that their sign is in the wrong location they would do well nothing This is the location where the sign should I know I have heard of Soda Springs but I guess I just didn t over to Idaho as much as I would have liked spending most of my time on the east side of the Tetons up in the Yellowstone park region and northwest of there where I spent my childhood in Missoula