I see some known ones, that aren't on the list. They might be too small.
You can see the red lines pretty starkly in the Midwest. The city I live in is 10% black, the other cities around are 5%. Less than three miles away, there are hole in the ground towns, where no one wants to live, still only 2% black. The place my parents grew up is 0.3% black. That place is much more liberal than the surrounding area, all the others could be considered sundown towns.
They are all concentrated here, and magically can't move out of this neighborhood. It is in the flood zone.
Edit: I just found a worse area nearby, one town is 15%, the only one near is 3%. Also a flood zone....