Louis-Joseph Gaultier de La Vérendrye (November 9, 1717 – November 15, 1761) was a French Canadian fur trader and explorer. Alongside his three brothers and his father, Pierre La Vérendrye, he advanced trade and exploration westward from the Great Lakes. He, his brother, and two colleagues are believed to be the first Europeans to cross the northern Great Plains and view the Rocky Mountains in Wyoming. Born in Quebec, Louis-Joseph joined the family fur trade business in 1735. He left Montreal with his father and journeyed west to Fort St. Charles on Lake of the Woods. He helped re-establish Fort Maurepas in 1736 and build Fort La Reine in 1738. From Fort La Reine, he and his father visited the Mandan Native Americans along the Missouri River in North Dakota later that year. In 1739 and 1740, he explored north from Fort La Reine, covering Lake Winnipeg, Lake Manitoba, Lake Winnipegosis, and the Saskatchewan River up to the area of present-day The Pas.

Louis-Joseph Gaultier de La Vérendrye - Wikipedia