HN has a policy against numbers in titles as they come off as link-baity...I wish a similar policy applied to titles with such absolute statements as "the best ever" or "what you never knew about..."
This map is not the "best" map ever of racial segregation, though it may be the most comprehensive. I'd argue that a more effective map would include some kind of time element, to show how formerly integrated areas slowly became segregated.
If that data could be collected/found/cross referenced. I doubt that is a possibility, and thus this probably is one of the 'best' maps of segregation (for some definition of best).
Also, this is what a history of segregation looks like. Its worth remembering that small towns, at least in places like Ohio, were so inhospitable to African Americans that they were referred to as "sundown towns" (http://en.wikipedia.org/wiki/Sundown_town ).
When people think that racism is over, maps like these serve as a pretty good starting point for asking them to reevaluate their POV.
Of course, there's always this you could start with too:
This map is not the "best" map ever of racial segregation, though it may be the most comprehensive. I'd argue that a more effective map would include some kind of time element, to show how formerly integrated areas slowly became segregated.