In 1738 he and son François traveled southwest to what is now North Dakota, arriving in December at a Mandan village a day's journey from the Missouri River.
Because of the difficulty of identifying places and Native American tribes in their reports, there is no certainty as to the route they took or how far they traveled, but they may have been the first European explorers to view the Rocky Mountains.
In 1738 the elder Verendrye and one son made a trip to within a day's journey of the Missouri River, and were the first white men to enter what is now North Dakota.
This was in the course of a journey from Verendrye's trading post in Manitoba, Canada, in an effort, which was unsuccessful, to reach the western sea by an overland route.However, later opinion suggested that the site was inaccurately located.
Ironically, new research indicates that Crow Flies High Butte may indeed be the site where the Verendryes climbed to view the Little Missouri Valley in 1742.