Here's a map that shows every person in America, and here are some interesting notes about it from Slate.com. This is a really interesting place to spend some time, especially if you keep your googlemaps open in a nearby tab. I found the expected level of segregation in my city (Chattanooga, TN):
But when I zoomed in as close as possible on my neighborhood (outlined in purple), I found a good bit of diversity:
I also took a trip up to my hometown in western New York (here is where I found googlemaps to be useful), and was puzzled by a very diverse patch of people just north of town (in the upper left of the image below).
It turns out that's the Buffalo Federal Detention Facility, built in 1997. Technically, it's about 30 miles east of Buffalo, in Genesee County, just outside the Batavia city limits. It's a US Immigration and Customs Enforcement Facility that holds people who have violated their immigration standing. And I had no idea it was there.