In 1728 there was a trader at Lake Nipigon—Sieur de la Verendrye, a Frenchman, to whom the natives told such positive tales about this great river flowing to the Sea of the West, that he determined to explore it.[53] He laid his plans before Beauharnois, then Governor of Canada, who was favourably impressed by the story, and also by a map which Verendrye's Amerind guide had drawn for him. An expedition of fifty men was fitted out, which left Montreal in 1731 under the command of Verendrye's sons and nephew. The party seem not to have moved directly for the river they intended to examine, but spent a number of years exploring, trading, and trapping in the North-west country. Finally, in 1738, they built an advance post, Fort La Reine, on the Assiniboine, whence they continued explorations north and south. In the latter direction they ascended the Souris, or Mouse, River, and at length arrived in the country of the Mandans, on the Missouri, at the great bend to the south, in what is now North Dakota, antedating in the region Lewis and Clark by over threescore years. This was in 1738. Again in 1742 the company arrived at the Missouri under the command of the eldest son and his brother, passed the Yellowstone River, and on January 1, 1743, came in sight of the Rocky Mountains, perhaps the Big Horn range, probably the first white men to see them from this direction; that is, north of about the 38th parallel, where the Spaniards had been. They climbed these mountains, and appear to have proceeded westward, perhaps as far as Wind River, where they remained some time in the country of the Snakes, hearing of another river farther south called Karoskiou, probably the head of the Colorado, now named Green River. They were then within about two hundred miles of the point reached, twenty-three years later, by Escalante, and not much farther from the locality on Grand River arrived at in 1765 by Don Juan Maria de Ribera.