neat-o interactive map of West Philadelphia

...not all of West Philadelphia, and not for every property on the map, but for most, you click on a property and bingo, you get information about all the people who ever lived in that house since the day it was built.

Even if you don't happen to be writing about Philadelphia, just following this kind of information can set a historical fiction writer's imagination a-boil.

http://poweltonvillage.org/interactivemap/

...so it got me thinking. Do other interactive maps like this exist in the interweb? How do you find them?

Wow! The colors alone tell a story.

Thanks, angelic2k