https://dc.urbanturf.com/articles/blog/anacostia-a-neighborhood-not-a-region/16368
Anacostia /ænəˈkɒstiə/ is a historic neighborhood in Washington, D.C. Its downtown is located at the intersection of Good Hope Road and Martin Luther King, Jr. Avenue. It is located east of the Anacostia River, after which the neighborhood is named. Like the other quadrants of Washington, D.C., Southeast encompasses many named neighborhoods, of which Anacostia is the most well known. Anacostia includes all of the Anacostia Historic District that was listed on the National Register of Historic Places in 1978. Often the name Anacostia is incorrectly used to refer to the entire portion of the city that is southeast of the Anacostia River. The Anacostia Business Improvement District is responsible for the development of the area.