Waterways define much of Illinois' borders and its commercial history.
* **Lake Michigan:** Forms the northeastern border, providing drinking water, recreation, and crucial shipping routes connecting to the St. Lawrence Seaway. * **Major Rivers:** The Mississippi River forms the entire western border, while the Ohio River and Wabash River form the southern and southeastern borders. * **Inland Rivers:** The Illinois River bisects the state, serving as a vital commercial link between the Great Lakes and the Mississippi River system. The Chicago River is famous for its architectural boat tours and being dyed green every St. Patrick's Day. * **Lakes:** The Chain O'Lakes in northern Illinois is a heavily used recreational waterway system.