ChicagoAncestors.org is a Google Maps mashup from the Department of Local and Family History of the Newberry Library, Chicago. The map is designed to help genealogists and local historians discover and share historical information about Chicago.
The site should be of huge interest to anyone who lives in Chicago or is interested in Chicago's past.
To use the map you can search for an address or just click on the map. The map then loads historical information for points around your selected location from a huge range of sources.
These sources include, amongst many more, Chicago Genealogist, Chicago Neighborhood Research Guide, Cushman Photographs, Digital Past, Great Houses of Chicago, Historic American Buildings Survey, Homicide in Chicago, New York Public Library Images and Jazz Age Chicago.
Back in the Day
If you are interested in Chicago's history you might also like this collection of historical photographs compared with the current view as captured by Google Street View. The site includes a small collection of historical photographs taken in Chicago.
SepiaTown is a another website that geo-tags historical photographs on Google Maps. The site has a few photographs of historical Chicago, although it's coverage is better in a number of other cities.