1890 Map of Illinois

Interesting 1890 map of Illinois from the David Rumsey Historical Map Collection, a large collection of online antique, rare, old, and historical maps, atlases, globes, charts, and other cartographic items.

1938-1941 Illinois Aerial Photographs

The Illinois Natural Resources Geospatial Data Clearinghouse, hosted by the Illinois State Geological Survey, has pretty complete and detailed aerial photographs taken between 1938 and 1941. These digitized photos have enough resolution to identify individual houses and see cars on the roads.

Illinois Historical Aerial Photography (ILHAP) project photos are available here:

http://www.isgs.uiuc.edu/nsdihome/webdocs/ilhap/launchims.html

1804-1891 Federal Township Plats of Illinois

It's interesting to see what local areas were like around the time the first settlers arrived. The State of Illinois has digitized plat maps available. Choose your county, then township, and browse to find what are probably the oldest available maps of the areas where you or your ancestors lived:

http://landplats.ilsos.net/Flash/FTP_Illinois.html

A searchable Illinois Public Domain Land Tract Sales database is here:

http://www.cyberdriveillinois.com/departments/archives/data_lan.html

A searchable database of Federal land conveyance records and images is here:

http://www.glorecords.blm.gov/