According to Wikipedia, the county was 77% white in 2010 and 13.6% black (about the same as the national averge).
I think the Democrats' long-term goal is to create metro-area governments that can take money from the suburbs to subsidize the central city. Then the only escape will be to live way out in the country.
Soon to arrive self-driving cars are in the news but self-flying airplanes are next. These will enable middle class families to live triple the distance from the nearest dirty, noisy, crime-ridden, drug infested, Democrat voting city work hub. Adjusting for speed differences, travel by airplane is the most energy efficient mode of transportation ever invented.