The first explorations of the country comprised within the present limits of the State of Montana are matters of great historic uncertainty. By one account it appears that, between the years 1738 and 1753, Pierre Gaultier de Varennes, the Sieur de la Verendrye, and his sons, particularly the Chevalier de la Verendrye, conducted parties of explorers westward, from Lake Superior to the Assinnaboine River, thence south to the Mandan country, and thence to the very sources of the Missouri. Even the date, January 12, 1743, is given for their first ascent of the Rocky Mountains. But such is the dearth of satisfactory evidence relating to these explorations, that positive inferences concerning them are impossible. The most that can be said is, that if De la Verendrye visited these regions, as is generally believed, to him doubtless belongs the honor of having adopted from original sources the name of the Yellowstone River. The goal of De la Verendrye's explorations was the Pacific Ocean; but the French and Indian war which robbed France of her dominion in America, prevented his ever reaching it. Following him, at the distance of nearly half a century, came the traders and trappers of the North-west Fur Company. As already noted, they were among the Mandans as early as 1797, and the name _Roche Jaune_ was in common use among them in 1804. They appear to have been wholly ignorant of the work of De la Verendrye, and it is quite certain that, prior to 1805, none of them had reached the Yellowstone River. Lewis and Clark particularly record the fact, while yet some distance below the junction of this river with the Missouri, that they had already passed the utmost limit of previous adventure by white men. Whatever, therefore, was at this time known of the Yellowstone could have come to these traders only from Indian sources.[D]