In 1938-1939 the Illinois State Planning Commission issued a series of 8 reports on major Illinois river basins to the Governor of Illinois, Henry Horner.  These reports were based on a standard outline from the Drainage Basin Study of the National Resources Committee, and include basic descriptions of the river and its tributaries, human occupancy and use, water development and hydrography flood control, groundwater, pollution, and the future development plans and needs.  All 8 reports were digitized through Google Books, and are freely available from the HathiTrust Digital Library.