Louis-Joseph Gaultier de La Vérendrye, explorer, cartographer, fur trader, military officer (born 9 November 1717 at Île aux Vaches, Quebec (New France); died at sea off the coast of Cape Breton 15 November 1761). Known by his title Chevalier, the youngest son of Pierre Gaultier de Varennes et de la Vérendrye led the first European exploration across the Missouri River into the Great Plains. He served New France in the War of the Austrian Succession and the Seven Years' War.
Louis-Joseph was the youngest of Pierre Gaultier de Varennes et de La Vérendrye’s four sons. The others were Jean-Baptiste Gaultier de La Vérendrye, Pierre Gaultier de La Vérendrye and François Gaultier de La Vérendrye (also known as François Gaultier Du Tremblay).
In 1735, Louis-Joseph joined his father's westward explorations. Following the death of his eldest brother Jean-Baptiste in 1736, he was sent by his father to re-establish Fort Maurepas (in Manitoba) and granted the title of Chevalier. He helped build Fort La Reine, a series of fur-trade posts located west of Winnipeg on the Assiniboine River, in 1738. That year, he accompanied his father to the Mandan country (near Bismarck, North Dakota) and in 1739, he was sent north to explore Lake Winnipeg. It is likely that he reached The Pas on the lower Saskatchewan River.
In 1742 Louis-Joseph, his brother François and two other Frenchmen undertook an epic 15-month journey southwest of the Mandan in search of the fabled "western sea." Having reached what were probably the Big Horn Mountains (Wyoming) they returned along the Cheyenne and Bad rivers and buried a lead plaque at Pierre (South Dakota), unearthed in 1913 and considered a historic treasure. After 1743, Louis-Joseph served as post commander at Chequamegon, Kaministiquia and Michipicoton.
As part of the war of the Austrian Succession (1744-48), Louis-Joseph participated in a brief military campaign against the Mohawk from January to March 1748 before leaving for the West again in June 1748 to care for his family’s fur trade empire. With the help of First Nations allies, in 1759 he participated in the defence of the Lake Champlain region during the Seven Years' War.
Considered an able commander and explorer, and the most active of La Vérendrye’s four sons, Louis-Joseph died in a shipwreck off the coast of Cape Breton in 1761. He had been on his way to France aboard the Auguste to settle family business after his father’s death.