By the golden age of the mountain man in the mid-19th-century, there were perhaps only 3,000 living in the West. Their origins were disparate, although they included many Anglo-Americans. A good number hailed from wilderness regions of Kentucky and Virginia and throughout the newly purchased Louisiana Territory, which occupied the entire central section of the continent. French Canadians traveled from the north to work in the fur trade, while Creole-Europeans represented approximately 15% of the men known to be living the isolated mountain life. Others were of Métis, Spanish, American, Black, Indian, and mixed-blood origin, most often Iroquois or Delaware. Most came to the West in their late adolescent years, the oldest learning the trade in their 30s. Many roamed the west for as long as their constitutions would hold up under constant attacks on their health and personal safety. Some stayed too long and failed to survive the experience. Among the most famous, Jim Bridger arrived at the age of 16, while Edward Robinson was eventually killed in his 60s by what were known as "bad snakes," a reference to the Snake tribe in Idaho country. Jim Beckwourth left the mountains at 68 and Old Bill Williams died at the age of 62 when a band of Utes "made him to come."

Most of the most notable frontiersmen traveled immense distances during their careers, and for many, only distant memories could recreate the routes taken. Few of the significant wilderness figures were experienced as cartographers to create accurate maps for industry, settlement, and the military. These American frontiersmen made first contact with numerous indigenous tribes in virtually every area of the west, but viable maps were few, and between such disparate cultures, relations could prove profitable or deadly at a moment's notice.