Google Earth is allowing its user to travel back in time, sort of. As of today, when you load Google earth you can choose to overlay a collection of historic maps. There are several to choose from including Lewis and Clark 1814(see picture above), world globe 1790, Tokyo 1680, and many more.

This marks another round in the competition between Microsoft and Google for their respective map software. Microsoft had recently released an update to their Virtual Earth software which included several rather high resolution 3D cities, with more on the way. The battle continues I guess.

Source: Google Blog