The Wabash River is a 475 miles (764 km) long river in the eastern United States that flows southwest from northwest Ohio near Fort Recovery, Ohio across northern Indiana to Illinois where it forms the southern Illinois-Indiana border before draining into the Ohio River, of which it is the largest northern tributary. From the dam near Huntington to its terminus at the Ohio River, the Wabash flows freely for 411 miles (661 km) which makes it the longest stretch of free-flowing river in the United States east of the Mississippi River.[citation needed]