Here's how neighborhoods west of Kenilworth Avenue in Northeast DC became isolated from the city – Greater Greater Washington
The neighborhoods of River Terrace, Parkside, Mayfair, Eastland Gardens, and Kenilworth in Northeast DC are isolated from the rest of the District by the Anacostia River to the northwest and DC Route 295 to the southeast. While these neighborhoods are very isolated and contain some of the lowest-income Census block groups in the District today, they were sited to take advantage of direct transportation routes to downtown and built for higher-income professionals.
Source: ggwash.org