Kankakee River, navigable stream rising near South Bend, northern Indiana, U.S., and flowing south and west approximately 135 miles (217 km) to be joined by the Iroquois River near Kankakee, Ill. It continues in a northwesterly direction to meet the Des Plaines River and to form the Illinois River. The Kankakee was first navigated by the French explorer Robert Cavelier, Sieur de La Salle, in 1679, when he descended the St. Joseph River, portaged to the Kankakee, and entered the Illinois River valley.