As mentioned by others, Journal of a Trapper by Osborne Russell, and an obscure one that I found a few years ago called Thirty One Years on the Plains and In the Mountains by William F. Drannan, written in 1899. I have a First Edition that is pretty much falling apart. He may be drawing the long bow in some places (but who am I to know?), but it is quite full of detail and covers the adventures of Drannan from 1847 to 1877 as a trapper and scout as well as part of his life afterward. It also gives a great deal of information about Kit Carson who gave Drannan his start as a frontiersman and was one of his closest friends.
:thumbsup: