Marys River (Illinois)

Marys River is a tributary of the Mississippi River in Illinois. It drains a small watershed between the Big Muddy River and the Kaskaskia River. It joins the Mississippi just southeast of Chester, near Kaskaskia. Because of its proximity to Kaskaskia — the capital of Illinois Territory and the first capital of the State of Illinois — Marys River was the site of early settlements leading into the interior of Illinois.

Marys River is approximately 41 mi in length.

Cities and counties
The following cities and towns are in the Marys River basin:
 * Steeleville
 * Sparta

Parts of the following counties are in the Mary's River basin:
 * Jackson County
 * Perry County
 * Randolph County