Index data (photograph center points) are offered by county in in ESRI Shapefile format. These data contain information for each aerial photograph, including the digital file name, flight line, county name, historic county code, roll and exposure numbers, agency which contributed the original photographic paper print for scanning, acquisition date and time (if available), the CD-ROM on which the original file is stored at the ISGS, and any additional notes.

Hard copy county indexes for aerial photography are housed at the University of Illinois Map and Geography Library. These indexes are either photo-mosaics of the prints for a single county (Photo Index), or drawn representations of approximate print locations (Line Index). Compressed digital versions of these indexes are available for viewing or download for each county. These indexes can be difficult to interpret. The majority of counties are depicted on one index sheet; some counties are divided into multiple sheets.