The Mississippi River forms the eatern border. The St. Frances River form a small part of the border on the northeast. The Red River forms a small part of the southwestern border.
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.
It is the Danube River.
The Ural Mountains, the Ural River, and the Caspian Sea form Europe's eastern boundary.
Red River
The Rio Grande River.
western
the Delaware river
The Ural Mountains and the Ural River in Russia are the mountains and river that form most of the northern boundary between Europe and Asia.
The Ohio river
The Ural Mountains form Europe's eastern boundary, the Volga River is a major river in that region, and the Caspian Sea lies to the east of that area.
The Clare river is a river running in the counties of Mayo and Galway. The main river in county Clare is the river Fergus. However, the river Shannon, the longest river in Ireland form the eastern boundary of county Clare and its estuary forms the southern boundary,
The Mississippi River forms the western boundary of Illinois.