The Mississippi Explorer is a term used to refer to three French explorers who explored the Mississippi River in the 17th century. The first explorer was Louis Jolliet, who was born in 1645 and was the first European to explore the Mississippi River. The second explorer was Hernando de Soto, who was born in 1539 and was the first European to cross the Mississippi River. The third explorer was Rene-Robert Cavelier, Sieur de La Salle, who was born in 1643 and was the first European to navigate the entire length of the Mississippi River.