[Liam]

Empires, Nations & Families: A History of the North American West 1800-1860 by Anne F. Hyde

This book documents the broad family associations that crossed national and ethnic lines and that, along with the river systems of the trans-Mississippi West, formed the basis for a global trade in furs that had operated for hundreds of years before the land became part of the United States. It shows how the world of river and maritime trade effectively shifted political power away from military and diplomatic circles into the hands of local people, and reveals how, in the 1850's immigrants to these newest regions of the United States violently wrested control from Native and other powers, and how conquest and competing demands for land and resources brought about a volatile frontier culture.

I haven't finished this, but it is fascinating and very well written.