River, flowing westward across Indiana, U.S. After crossing Indiana, the Wabash forms the 200-mi (320-km) southern section of the Indiana-Illinois boundary below Terre Haute, Ind.
It empties into the Ohio River in southwestern Indiana after a course of 475 mi (764 km). During the 18th century the French used it as a transportation link between Louisiana and Quebec. After the War of 1812 , its basin was rapidly developed by settlers. After the coming of the railroads in the 1850s, navigation almost disappeared except for barge traffic on its lower course.