La Vérendrye has established posts at Rainy Lake, the Lake of the Woods, Lake Winnipeg, the Red River, and the Assiniboine River by 1738.

Although unable to discover a river flowing toward the fabled Western Sea, his impressive gains as a fur-trader persuade the French minister of the marine, Jean Frederic, comte de Maurepas, that his true interest is commercial gain, over the advancement of knowledge.

La Vérendrye visits the Mandan villages on the Missouri River in modern North Dakota late in the year, entering the main village accompanied by six hundred Assiniboines and thirty Mandans flying the French colors and beating drums.