Marys River (Illinois) River basin: 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 in length. The following cities and towns are in the Marys River basin: Parts of the following counties are in
River Grove, Illinois River Grove, Illinois River Grove is a village in Cook County, Illinois, United States. The population was 10,227 at the 2010 census. River Grove is located at (41.925830, -87.840135). According to the 2010 census, River Grove has a total area of , all land. Just as nearby Elmwood Park and Oak Park are named after their historic elm and oak trees, River Grove gets its two-part name first from the community's shallow muddy plains river, and second from the majestic groves of American ash trees lining shore of the (Aux) Des Planes River "Bottomland." Credit goes to the village's early