Across The Wide Missouri - Bernard DeVoto

>The book chronicles the competition between John Jacob Astor's American Fur Company and the Rocky Mountain Fur Company, an "opposition" group of trappers (including Jim Bridger and Kit Carson) descended from the earlier entrepreneurial activities of General William H. Ashley. Devoto specifically narrates the major expeditions and the daily experiences of the Western divisions of these companies, which scoured the northernmost regions of the Rocky Mountains for beaver.

https://www.goodreads.com/book/show/831175.Across_The_Wide_Missouri