They were part of a process that added Western Canada to the original New France territory that was centred along the Saint Lawrence basin.

In the 1740s, two of his sons crossed the prairie as far as present-day Wyoming, United States, and were the first Europeans to see the Rocky Mountains north of New Mexico.

In 1704 and 1705 La Vérendrye took part in the raids of Queen Anne's War, which was waged by colonists in the English and French areas of North America.

At age 22, he enlisted in the French Army, and fought in Flanders during the War of the Spanish Succession; he was seriously wounded at the Battle of Malplaquet.

After recovering from his injuries and being given paroled as a prisoner of war, Gaultier returned to Canada and married Marie-Anne, daughter of Louis Dandonneau, Sieur Du Sablé, in 1712.

La Vérendrye began trading in the area and in 1728 was appointed as commandant when his brother left to fight the Fox Indians.

At this time people thought that not far to the west was an inlet from the Pacific called the mer du couchant, similar to the equally mythical Strait of Annian.

In 1717 Zacharie Robutel de La Noue tried to reach Rainy Lake but succeeded only in establishing Fort Kaministiquia.

The British on Hudson Bay heard reports of coureurs des bois west of Lake Superior, but they left no records in the French archives.

According to Pehr Kalm, La Vérendrye was acting upon orders given by de Beauharnois to explore until he could reach the ocean.

He along with 20 other Frenchmen, 19 voyageurs including the Jesuit missionary priest Jean-Pierre Aulneau who accompanied them, were killed by the Sioux on Massacre Island in Lake of the Woods.

[4] La Vérendrye restrained the local Cree from a war of revenge in order to protect the fur trade.

Joining a large band of Assiniboines, he pushed southwest across the prairie and reached a Mandan village probably somewhere near the modern New Town, North Dakota, about 70 miles east of the Montana border.

In order to get rid of their numerous Assiniboine guests, the Mandan claimed that there was a Sioux war party in the area.

From Fort La Reine he sent his son Louis-Joseph exploring westward as far as, probably, the Big Horn Mountains of Wyoming (1742–43).

Back in France, Maurepas was growing increasingly irritated with La Vérendrye, who he thought was trading in furs when he should be exploring.

He returned to New France and led the life of a gentleman while doing a considerable business since his sons remained as traders in the west.

In 1756 the western command was given to Pierre's son Louis-Joseph Gaultier de La Vérendrye, but he was unable to travel to the west.