What difference did it make whether any of the sources of Maria's river lay near the 50th parallel? Why was it so important that Meriwether Lewis was willing to risk his life in a region occupied by the "Pahkees" or Minnetares, the Assiniboines, and other people whom he had been led–by their enemies, of course–to believe were "vicious and illy disposed"?1
Thomas Jefferson's instructions had not included this plan. Indeed, the President had directed Lewis only to inquire into the southern sources of the Missouri, pointing out that "the Northern waters of the Missouri are less to be enquired after, becaue [sic] they have been ascertained to a considerable degree, & are still in a course of ascertainment by English traders, and travellers."2 The initial reports Lewis wrote to Jefferson after the expedition's return to St. Louis in late September of 1806 said nothing of his foray into Blackfeet territory, much less his own hairbreadth escape from death.
1. Lewis, May 10, 1805. He was here referring specifically to the Assiniboines.
2. Donald Jackson, ed., Letters of the Lewis and Clark Expedition with Related Documents, 1783–1854, 2nd ed., 2 vols. (Urbana: Uiversity of Illinois Press, 1978), 1:61–63.
3. Ibid., 1:341. In the spring of 1810, during his conversations with Nicholas Biddle preparatory to the latter's editing of the captains' journals, Clark reiterated that explanation (Ibid., 2:544), which Biddle transcribed as follows: "July 20, 1806. The reason why it was wished that Maria's river should extend to 50° north was that as our boundary is to be formed by a line due west from lake of the Woods to the Mississi., & the Mississi. river not answering that purpose it was hoped that a river parallel to it would go far enough north to satisfy the treaty boundary the lake of Wds. being 49° 37 Minutes at its northern extremity."