The Ohio River
The Rio Grande.
The Ohio River forms Ohio's southern border.
The Ohio River forms the southern borders of Ohio and Indiana.
The Ohio River is the southern boundary of Ohio and Indiana.
The Ohio river is located on the southern boundary of Indiana and Ohio. The Ohio River also borders northern Kentucky.
The Ohio River forms the southern boundaries of Ohio and Indiana. It begins at the Ohio-Pennsylvania border. It flows southwesterly between Ohio and Kentucky, Indiana and Kentucky, and continues to the Mississippi River.
none of the rivers form the southern border of Indiana, but the Ohio river forms the southern border of Ohio.
The Ohio River is south of Indiana and forms the boundary between Indiana and Kentucky.
The Ohio River and Ohio River Valley boarder the southern part of Ohio.
Columbia
The Wabash River forms the southern portion of Indiana's western border. The northern portion of Indiana's western border is simply a straight line marked on the map. The southern border of Indiana is also a river - the Ohio.