The Rocky Mountains skirting this country on the East, dwindle from stupendous heights into sloping ridges, which divide the country into a thousand luxurious vales, watered by streams which abound in fish. The most remarkable heights in any part of the great backbone of America are three elevated insular mountains, or peaks, which are seen at the distance of one hundred and fifty miles: the hunters very aptly designate them the Pilot Knobs they are now generally known as the Three Paps or ‘Tetons’; and the source of the Great Snake River is in their neighborhood.... Boiling fountains, having different degrees of temperatures, were very numerous; one or two were so very hot as to boil meat. In other parts, among the rocks, hot and cold springs might alternately be seen within a hundred yards of each other, differing in their temperature. McKenzie’s exact route can only be conjectural, but the context suggests passage through Jackson’s Hole into a corner, at least, of Yellowstone Park. It was apparently on this occasion that the “Trois Tetons” and “Pierre’s Hole” were given their names by Iroquois or French-Canadians who accompanied McKenzie. Chittenden reports the discovery in 1880 by Colonel P. W. Norris of a tree near the Upper Falls of the Yellowstone with the inscription “JOR Aug 19 1819.” Although of course the initials prove nothing as to identity, Chittenden accepts this as proof of white men in the Park at that time. Stimulated by McKenzie’s success in acquiring peltries, the Northwest Company followed up with other Snake River expeditions. The threat of British domination of Oregon was aggravated when, in 1821, the Northwest Company was absorbed by the powerful Hudson’s Bay Company. Shortly after the consolidation of the British companies, the prospects for a revival of American interest in the mountain fur trade were awakened in the frontier town of St. Louis by the formation of a partnership that would evolve into the Rocky Mountain Fur Company. In 1822 General William H. Ashley and the veteran Major Andrew Henry enlisted the aid of “one hundred young men to ascend the Missouri River to its source” on a trapping expedition. Among those who joined the enterprise, then or subsequently, were men destined to make history in the West—James Bridger, Thomas Fitzpatrick, Jedediah Smith, William Sublette and David E. Jackson. They were green boys, hardly fit material for an epic invasion of the uncharted Rocky Mountains; yet they were destined to become continental explorers.