Here are some good resources for information on Chicago and Illinois.

Encyclopedia of Chicago History 

http://encyclopedia.chicagohistory.org

Chicago's history provided by the Chicago History Museum, the Newberry Library and Northwestern University.

Illinois Maps and Census Information 

http://www.illinoisatlas.com

A collection of Illinois maps based on census information and links to sites about the state.

Chicago Public Library

http://www.chipublib.org/search/catalog/

Go to Chicago's public libraries without leaving your seat!