What is the theme in Jim Bridger, Mountain Man; a Biography by Stanley Vestal?

Jim Bridger seeks adventure and profit in the wilderness, but he is also an important part of the development of the United States. The beaver trapping business opens up the frontier area of the sources of the Missouri River to American settlement. Indians live there but at a very low level of population density. By and large, the white trappers try to get along with the Indians. Squaw men marry Indian women and join Indian tribes. Many other white men and some black or mulattos also intermarry with Indian women but live on the frontier in their own forts. As the beaver trade declines, Jim's activity shifts to helping ordinary settlers cross the United States to move to Oregon and California. Even the Mormons, though hostile, settle in the Utah Territory. Many people receive advice from Jim Bridger, and most that do not listen to him regret it.