Early in the Nineteenth century, the mountain men emerged as a small but distinctive group whose knowledge and experience of the Transmississippi West extended the national consciousness to continental dimensions. Though Lewis and Clark blazed a narrow corridor of geographical reality, the west remained largely terra incognita until trappers and traders -- Jim Bridger, Kit Carson, Tom Fitzpatrick, Jed Idiah -- opened paths through the sun-choked mountain wilderness. Collectively, they came to know every stream, mountain crag, canyon cataract, waterless stretch of plain, refuge of game, hostile Indian hideout.
By the time the beaver market collapsed in the early 1840s, the mountain men's remarkable familiarity with the land provided a map to the Rockies, the Great Plains, the Mexican southwest, the disputed Oregon Territory, and California. They had already helped the first missionaries across the continent to lay groundwork for the wagon trains that followed. They opened the way west to Frimont and played a major role in the pivotal years of 1845 to 1848, when Texas was annexed, the Oregon question decided, and the Mexican War ended with the southwest and California in American hands and the Pacific Ocean our western boundary.