This is a very pretty neighborhood. I expect it was gentrified sometime in the past. The H street nearby has hints that it may still be upgrading (seems like there is a large new apartment building). The restaurants there (several are vegetarian/vegan) are very handy, as is the Whole Foods about two blocks further East from 4th Street along H.
Lastly, the nearness to Union Station (which has a Red Line Metro stop, which connects to three other color lines only two stops towards town) is fantastically convenient, in my opinion.