ISU Iowa Geographic Map ServerISU's Map Server contains historical maps (the 1836-1859 General Land Office survey and the 1875 Andreas Atlas), aerial photos from the 1930s through the 1980s, current USGS topographic maps, and more.
From the IGMS website: "This site provides free access to Iowa geographic map data through an on-line map viewer and through Web Map Service (WMS) connections for GIS. The site was developed by the Iowa State University Geographic Information Systems Support and Research Facility in cooperation with the Iowa Department of Natural Resources, the USDA Natural Resources Conservation Service, and the Massachusetts Institute of Technology."