For those interested in the fur trade, check this site, and especially
note the presence of online historical books and archival documents:
 
Mountain Men and the Fur Trade: Sources of the History of the Fur Trade
in the Rocky Mountain West <http://www.xmission.com/~drudy/amm.html>
     This is an on-line Library and Research Center devoted to the
history, traditions, tools, mode of living, etc., of the trappers,
explorers, and traders known as the Mountain Men.  LAR