Which French explorer claimed the Mississippi River for France?

Robert de La Salle is the correct answer because he is known for leading an expedition that traveled the length of the Mississippi River and officially claimed it for France in 1682. His exploration established France's territorial claims in the region, which were significant in the context of early North American colonial expansion. La Salle's journey culminated in a ceremony where he proclaimed the entire Mississippi River watershed as "Louisiana" in honor of King Louis XIV. This claim helped to solidify French influence in the interior of North America, which became crucial for trade and settlement in the ensuing years.

The other explorers mentioned made important contributions to mapping and exploring North America. Jacques Cartier explored parts of Canada and the St. Lawrence River but did not reach the Mississippi. Samuel de Champlain is best known for founding Quebec and his extensive exploration of the Great Lakes but also did not claim the Mississippi. Louis Jolliet was an explorer who accompanied Jacques Marquette on a significant expedition down the Mississippi, but he did not make the claim for France; that was La Salle's achievement.