The maps at U of I are wonderful.  I particularly liked the digitized maps so I could find my ancestors farms. The Hixson Plat Book, 1930 http://digital.lib.uiowa.edu/cdm4/index_hixson.php?CISOROOT=/hixson has some very clear maps with very legible handwriting.  I also found the Iowa Historic Atlases from the late 1800's to early 1900's http://digital.lib.uiowa.edu/cdm4/index_maps.php?CISOROOT=/maps very useful. Jean Perera