More recently, the Google Maps API has encouraged a number of organizations, developers, and even individuals like you and me, to create historic overlap maps for the online tool Google Maps (nice for people who don't want to download the Google Earth software). 120 historical maps from the David Rumsey Map Collection, for example, were integrated into Google Maps last year. Additional historic map overlays you might want to explore, include:
- North Carolina Historic Overlay Maps - Selected maps from the North Carolina Maps project
- Scotland Historical Map Overlays - Ordnance Survey maps and large-scale town plans from the National Library of Scotland
- Henry Hudson 400 - Historic overlays includes historical maps of early New York and Amsterdam as part of a project to celebrate the voyages of Henry Hudson.
- Greater Philadelphia GeoHistory Network - Visit the Interactive Maps Viewer to view selected historic maps and aerial photographs, overlayed with current data from Google Maps. The "crown jewel" is a full-city mosaic of the 1942 Philadelphia Land Use Maps.
- Singapore Historical Maps - This isn't an overlay, but combines a map with historic photos of Singapore places in an interesting way.
If you really love these historic overlay maps, you may want to download the free Google Earth software. There are many more historic map overlays available through Google Earth, than through Google Maps, including many posted directly by Google. You can find the historical maps in the sidebar section titled "layers."
Related: Make Your Own Google Map