Ohio River course forms the northern borders of West Virginia and Kentucky; and the southern borders of Ohio, Indiana and Illinois, until it joins the Mississippi River at the city of Cairo, Illinois. Where the Ohio joins the Mississippi is the lowest elevation in the state of Illinois, at . The Ohio River, which flows westward from Pittsburgh, Pennsylvania, to Cairo, Illinois, is the largest tributary, by volume, of the Mississippi River in the United States. At the confluence, the Ohio is considerably bigger than the Mississippi. Measured by long-term mean discharge in cubic feet per second and cubic meters per second,
Vermilion River (Illinois River) in Illinois. Access to a stretch of river around a dam owned by Buzzi Unicem was temporarily barred in 2009 after two drowning deaths that occurred on June 23 and 26, respectively, as well as numerous other boating accidents. The river access was reopened in 2010. The following cities and towns are drained by the Vermilion: The following counties are drained at least in part by the Vermilion River: Vermilion River (Illinois River) The Vermilion River is a tributary of the Illinois River in the state of Illinois, United States. The river flows north, in contrast to a second Vermilion