Which French explorer explored the Mississippi River to its mouth in 1682?

René-Robert Cavelier, Sieur de La Salle, explored the Mississippi River to its mouth in 1682. Leading a French expedition, La Salle traveled down the lower Mississippi and reached the Gulf of Mexico on April 9, 1682.

At the river’s mouth, La Salle claimed the Mississippi basin for France and named the vast territory Louisiana in honor of King Louis XIV. The expedition strengthened French claims across the interior of North America, even though France initially established relatively few permanent settlements there.

Louis Jolliet and Jacques Marquette had explored a substantial section of the Mississippi several years earlier, reaching the mouth of the Arkansas River and helping confirm the river’s course. They did not complete the descent to the Gulf. La Salle’s achievement was therefore the final passage to the mouth and the formal claim of the river basin for France.