In the mean time, from St. Louis as a center, American fur-traders, the advance-guard of settlement, were penetrating into the heart of the vast wilderness between the Mississippi and the Pacific coast. [Footnote: Chittenden, Am. Fur Trade of the Far West] This was a more absolute Indian domain than was the region between the Alleghenies and the Mississippi at the end of the seventeenth century--an empire of mountains and prairies, where the men of the Stone Age watched with alarm the first crawling waves of that tide of civilization that was to sweep them away. The savage population of the far west has already been described in an earlier volume of this series.[Footnote: Farrand, Basis of Am. Hist. (Am. Nation, II.), chaps, viii., ix., xii.; see also chap. iv. On the location of the Indians, see map, p. 309; Chittenden, Am. Fur Trade, II., pt. v., chaps, viii., ix., x.; Bureau of Ethnology, Seventh Annual Report.]

With the development of the Rocky Mountain Fur Company, the most flourishing period of the St. Louis trade in the far west began. The founder of this company was William H. Ashley, a Virginian. Between the autumn of 1823 and the spring of the next year, one of his agents erected a post at the mouth of the Bighorn, and sent out his trappers through the Green River valley, possibly even to Great Salt Lake. A detachment of this party found the gateway of the Rocky Mountains, through the famous South Pass by way of the Sweetwater branch of the north fork of the Platte. This pass commanded the routes to the great interior basin and to the Pacific Ocean. What Cumberland Gap was in the advance of settlement across the Alleghenies, South Pass was in the movement across the Rocky Mountains; through it passed the later Oregon and California trails to the Pacific coast.

On the lower Missouri and at various places in the interior,[Footnote: See map, p. 114; Chittenden, Am. Fur Trade, I., 44-51 (describes posts, etc.).] stockaded trading-posts were erected by the Rocky Mountain Fur Company and its rival, the American Fur Company. In these posts the old fur-trade life of the past went on, with French half-breed packmen and boatmen, commanded by the bourgeois. But in some of the best trading-grounds, the savages declined to permit the erection of posts, and so, under Ashley's leadership, bands of mounted American trappers, chiefly Kentuckians, Tennesseeans, and Missourians, were sent out to hunt and trade in the rich beaver valleys of the mountains. The Rocky Mountain trappers were the successors to the Allegheny frontiersmen, carrying on in this new region, where nature wrought on a vaster plan, the old trapping life which their ancestors had carried on through Cumberland Gap in the "dark and bloody ground" of Kentucky.