The Wabash River forms the easter border of Illinois. I've noticed that the previous answer was the Ohio River. The Ohio River actually is what runs along the southern tip of Illinois.
Ohio River
The Mississippi River forms the wavy western border of Illinois. And the Ohio Wabash River is the southern border of Illinois.
Illinois is closer to the Ohio River than Georgia. The Ohio River forms the northern border of Kentucky, which is adjacent to Illinois. In contrast, Georgia is located much further south and does not border the Ohio River at all.
Illinois and Kentucky. Illinois is north of the Ohio River and east of the Mississippi river. Kentucky is south of the Ohio River and east of the Mississippi River.(Missouri is on the west bank of the Mississippi and does not border the Ohio River.)
Illinois and Kentucky. Illinois is north of the Ohio River and east of the Mississippi river. Kentucky is south of the Ohio River and east of the Mississippi River.(Missouri is on the west bank of the Mississippi and does not border the Ohio River.)
wabash
The Mississippi River is the largest river and it is the western border of Illinois. The Ohio and Wabash Rivers are the southern border of Illinois. The Illinois River is the largest internal river in Illinois.
Illinois is bordered by the Ohio River to the south.
Starting in western Pennsylvania, the Ohio River borders Ohio, West Virginia, Kentucky, Indiana, and Illinois. The Ohio River does not border 44 States.
Ohio
The 3 states that the Ohio River borders are,Ohio, Indiana and Illinois.