>>2703256Thats is an easy but worthy favorite. Very fun to read all the various journals and diaries of the participant. Some of the landscapes they traveled havent changed all that much.
But for me its John Colter- who was a member of the L&C expedition but was allowed to quit on their way back and return up toward the headwaters of the Missouri and eventually the Yellowstone. First white man to see the grand tetons supposedly
https://en.wikipedia.org/wiki/John_Colter 
