Marys River (Illinois) 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 the Mary's
Big Wood River receives the tributary streams of Warm Springs Creek and Trail Creek. Below Ketchum, it is joined by the East Fork Wood River at Gimlet before passing by the small cities of Hailey and Bellevue. Continuing south, the river enters the Wood River Valley, the northern part of Magic Valley, after which it flows into Magic Reservoir. A tributary stream, Camas Creek, joins the river in Magic Reservoir. Below Magic Dam, the Big Wood River enters Lincoln County, passing by many lava beds and irrigation canals before entering Gooding County. Just west of Gooding, the Big Wood River joins the Little