Upon their return trip in 1806, after wintering at Fort Clatsop at the mouth of the Columbia, Lewis and Clark divided in order to explore the country more thoroughly, the latter undertaking to determine the source of the mysterious Yellowstone. On July 15, with eleven white men, the Indian woman Sacajawea and her baby, the cavalcade crossed Bozeman Pass, which marks the divide between the Yellowstone and Gallatin Fork, and reached the vicinity of present Livingston, Montana. Never suspecting what wonders lay concealed behind the snowy mountain wall to the south, Clark hurried on down the river to rejoin Lewis, with glory enough for one expedition. There is only one hint of volcanic phenomena which Clark seems to have obtained from any source other than the presumed conversation with Colter, mentioned below. This was an Indian tale, received after Clark’s return, but before Colter’s return, to the effect that at the head of Tongue River, a branch of the Yellowstone, “there is frequently heard a loud noise like Thunder, which makes the earth Tremble, they state that they seldom go there because their children Cannot sleep—and Conceive it possessed of spirits, who were averse that men Should be near them.” Speculates Vinton, “it can hardly be doubted that the Indians referred to the geyser basin in the Park,” rather than to the Tongue River neighborhood. It is commonly supposed that, prior to Colter, no white man had knowledge of strange phenomena on the Upper Yellowstone, this supposition being one of the pillars of the “first-discovery” theory. It is fairly evident that Clark knew nothing of geysers when he was within seventy-five miles of them in 1806 but, ironically enough, at this time some intimation of them had certainly reached others, including Clark’s sponsor, Thomas Jefferson. On October 22, 1805, James Wilkinson, governor of Louisiana Territory, with headquarters in St. Louis, sent to the President, in care of Captain Amos Stoddard, a Savage delineation on a Buffalo Pelt, of the Missouri & its South Western branches, including the Rivers plate & Lycorne or Pierre jaune; This Rude Sketch without Scale or Compass ‘et remplie de Fantaisies ridicules’ is not destitute of Interests, as it exposes the location of several important Objects, & may point the way to useful enquiry—among other things a little incredible, a volcano is distinctly described on Yellow Stone River. Wilkinson apparently obtained this primitive map from unidentified traders. It could not have been a copy of Clark’s map sent from Fort Mandan the April previous, for it obviously contained new data. In an advice to Henry Dearborn, Secretary of War, dated September 18, 1805, Wilkinson revealed that his interest in Yellowstone curiosities was sufficiently aroused to dispatch an expedition of his own upriver!