Rumsey Historical Maps Integrated Into Google Maps

Elisabeth Grant at the American Historical Association's AHA Today points out that there is a Google Earth/David Rumsey Historical Map Collection mashup. The mashup puts the historical map on top of the current Google map.

For example, you can see what Washington, DC looked like in 1851 on top of Washington, DC today. In the upper right-hand corner, you make the historical map fade in and out to pinpoint it against today's buildings.

There do seem to be problems opening some of the maps. So, it's not perfect, but those without problems sure are fascinating (like Japan in 1694)!