GeoTIFF files are in the following coordinate system:

State Plane Cooridinate System 1983 - Iowa North (1401) - in meters - for all counties in the north plane

State Plane Cooridinate System 1983 - Iowa South (1402) - in meters - for all counties in the south plane

Please Note:
GeoTIFFs have a LZW compression. Arcview 3.3 does not read images with this compression.