Other than being the capital of the U.S., D.C. is known for having a predominantly Black population (not counting those that live in the outside suburbs, but go to work in the city). From this large Black population, D.C. has developed a very distinctive culture including its Go-Go music, mambo sauce, and style of dress for the younger population (a style that is very different from other metro areas that imitate NYC for the most part). And, like many other large metro area, the people here have a their own slang and accent, one that is cross-bred from both the South and the North. Despite the recent developement projects going on there, the SouthEast section of DC is popularly known as the most dangerous area of the town. In addition, many long-time DC residents have been moving to the bordering counties such as Prince George's County, MD, Charles County, MD, and Alexandria, VA.
I can tell you're from Washington DC, because you're accent doesn't have a heavy drawl like the Dirty South, but it definitely ain't New York or Philly.