The Rock Creek Park divide is just as noticeable on the map as it is driving around the area. On a larger scale, the SE/NW divide is exactly what you'd expect. Keep in mind that the city itself is (or at least was, before gentrification) predominately black, and the SE areas are the poorest.
What would make the DC map even more interesting would be to watch it over time as more "blue" moves into those "green" areas around Columbia Heights, Petworth, Shaw etc.