毛皮貿易
Fur trappers, often working for fur traders, followed nearly all possible streams looking for beaver in the years (1812–40) the fur trade was active. Fur traders included Manuel Lisa, Robert Stuart, William Henry Ashley, Jedediah Smith, William Sublette, Andrew Henry, Thomas Fitzpatrick, Kit Carson, Jim Bridger, Peter Skene Ogden, David Thompson, James Douglas, Donald Mackenzie, Alexander Ross, James Sinclair, and other mountain men. Besides discovering and naming many of the rivers and mountains in the Intermountain West and Pacific Northwest, they often kept diaries of their travels and were available as guides and consultants when the trail started to become open for general travel. The fur trade business wound down to a very low level just as the Oregon trail traffic seriously began around 1840.