Who first traced the route of the Mississippi River?

The Spanish explorer Hernando de Soto was, in 1541, the first white man to see the Mississippi, but it was not until June 1673 that two Frenchmen, Louis Jolliet and Jacques Marquette, actually explored the river in canoes. They travelled far enough south to prove that it emptied into the Gulf of Mexico and could not, therefore, be the hoped-for North-west Passage.