Long the dominant icon embodying the spirit of America's frontier past, the image of the cowboy no longer stands alone as the ultimate symbol of independence and self-reliance. The great canvas of the western landscape-in art, books, film-is today shared by the figures called "Mountain Men." They were the trappers of the Rocky Mountain fur trade in the years following Lewis and Clark's Expedition of 1804-1806. With their bold journeys peaking, during...