Mississippi river
The Mississippi River forms the western boundary of the State of Illinois.
The Mississippi River forms the western border of Illinois.
Mississippi river
The Mississippi River forms the western boundary of Illinois.
The Ohio River forms the western boundary of West Virginia.
Missisippi
western
The Mississippi river forms the boundary between Missouri and Illinois!
Two rivers partially form Illinois State's Eastern boundary. The Wabash River is one river that forms Illinois' boundary. The Ohio River is the other river that forms the state's boundary.
Ohio River
The Wabash is the longest river in Indiana. It flows from Ohio across northern Indiana until it forms the border between Indiana and Illinois.