The Rumsey collection includes 16 maps. Among them you'll find a 1790 world globe, a 1680 map of Tokyo, and an 1814 map spanning the Pacific Ocean to the Mississippi--courtesy of Lewis and Clark.
To view these new old maps, you'll need the latest version of Google Earth (use the program's check-for-updates feature if you're not sure you have it). In the layers section, select All Layers, then look for Featured Content > Rumsey Historical Maps. This may just be the coolest Google Earth feature ever.