Add your own black squirrel sighting to this map: click this link, then follow the instructions at Google Maps
You should be able to see markers on this map showing where black squirrels have been sighted. If you don't see any of the markers, try refreshing the page, or blame Google Maps. I'm principally interested in the black squirrel ranges in the US, but sightings anywhere in the world are welcome.
Can't post to the map for some reason? Just tell us where your sighting was in the comments.