I found a color map showing the chocolating of DC.
The purple shows areas that are 75% and above AfrAm. The TC and other areas in red are between 50 and 74.9% AfrAmer, and the other colors are explained in the legend. I'm gonna guess no color means less than 20% Black, which geographically looks like most of the District.
I'm looking at my 1938 block by block segregation map of SW DC and this map and trying to figue out where 4th Street SW falls, as that appears to be the dividing line from the mainly white part of SW and the black part. Regardless, a lot of it was leveled with the Southwest Urban Renewal project.