Rising in western Ohio, the Wabash River flows northwestward into Indiana, where it passes south of Ft. Wayne. Ninety miles from its source, the river's flow is blocked by the Huntington Dam; below that structure, the Wabash continues westward to Lafayette and then southward to Terre Haute. Below the latter city, the river angles SSW, forming a 200 mile border between Indiana and Illinois before entering the Ohio.
Major tributaries from the north include the Little and Tippecanoe Rivers in Indiana and the Vermillion, Embarrass and Little Wabash Rivers in eastern Illinois; the primary tributaries from the east are the Wildcat, White and Patoka Rivers, which drain most of central Indiana. The Wabash watershed covers 66% of Indiana and the river's segment below the Huntington Dam, more than 400 miles in length, is the longest stretch of free-flowing river east of the Mississippi; indeed, the Wabash is the largest south-flowing tributary of the Ohio River.
Of more significance to naturalists, the Wabash watershed is renowned for its biological diversity. According to the Nature Conservancy, this river system harbors five of the forty most diverse river segments in the United States. At least 150 species of fish and 50 species of freshwater mussels inhabit this riverine ecosystem where a host of private, public and conservation organizations are working to protect and restore its vast network of floodplain woodlands and wetlands.
