Statewide Illinois Library Catalog (SILC)

Great for finding books at Illiois libraries. Most libraries will do inter-library loans.

http://findit.ilsos.net/OCLC/

"The Statewide Illinois Library Catalog, known as SILC, is Illinois' first all inclusive statewide union catalog that integrates WorldCat and the Illinois Library Systems' local consortial OPACs, to provide both shelf status and interlibrary loan capabilities in a single searchable interface. SILC resides on the familiar FirstSearch platform as an additional WorldCat database that allows users to scope to regional groups within Illinois, as well as by type of library. From a single WorldCat record, users will be able to link to a local shared catalog record to see if and where an item is available for loan."

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/