William Clark and his contingent of the Corps of Discovery explored the Yellowstone River from July 15 to August 3, 1806, from the Big Bend at today's Livingston, Montana, to its mouth. The first white men to see any part of the Yellowstone River may have been the French explorers Louis and François La Vérendrye, who seem to have gotten within sight of the Bighorn Mountains in the summer of 1742 before abandoning their effort to find a waterway from eastern Canada to the Pacific Ocean. Next came Pierre Ménard, a French Canadian trader who claimed to have been on the Yellowstone sometime before 1795. Another trader by the name of Charles Le Raye is said to have traveled as far as the mouth of the Bighorn River in 1802, though there is some doubt about the authenticity of the report attributed to him.1 Fourth in line was François-Antoine Larocque (1784–1869), who is important to the story of Lewis and Clark on the Middle Missouri for several reasons.
• He made two trips from Fort Assiniboine to the Mandan villages, in 1804 and 1805, and wrote concise descriptions of his experiences, although the purpose of his trips was essentially commercial. (He also wrote the first detailed ethnographic description of the Crow Indians and their culture, comparing them with the Mandans and Hidatsas.)
• On his first trip, in the fall of 1804, he met Lewis and Clark, and his journals, as well as those of his companion, Charles McKenzie, contain a unique slant on certain aspects of the expedition and its commanders.
• On his second trip he joined a group of homeward-bound Crow Indians at the Mandan villages, and arrived at the Yellowstone via the Mampoa, or Shot Stone River—which Clark was to call Pryor Creek—via a southern overland route, thereby preceding Clark on the Yellowstone by 10 months and 15 days.
• The account of his return trip down along the Yellowstone that fall, though containing some possible errors and a few obvious omissions, suggests what Nathaniel Pryor would have faced had he been ordered to follow the Yellowstone and Missouri to the Mandan villages.2
1. A. P. Nasatir, ed., Before Lewis and Clark: Documents Illustrating the History of the Missouri, 1785–1804 (Bison Book edition, 1990; 2 vols., Lincoln: University of Nebraska Press, 1958), 1:31–33, 110.
2. Francois-Antoine Larocque's "Missouri Journal" and "Yellowstone Journal" are in W. Raymond Wood and Thomas D. Thiessen, Early Fur Trade on the Northern Plains: Canadian Traders Among the Mandan and Hidatsa Indians, 1738-1818 (Norman: University of Oklahoma Press, 1985), 133–220. Larocque's journals were first published in an incomplete and inaccurate French edition in 1889-90. The edition by Wood and Thiessen is the first complete version in English. For a brief biography of Larocque, and the history of his journals, see pages 129-32.