In its upper course in Shelby County, the river is dammed to form Lake Mattoon and collects the short West Branch Little Wabash River, which flows for its entire length in Shelby County. Other tributaries include the Fox River, which joins it in Edwards County; the Elm River, which joins it in Wayne County; and the Skillet Fork, which joins it in White County.
^U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2012-03-29 at the Wayback Machine, accessed May 19, 2011