We went here last week, finally. This one is easier to drive to than to Metro to so I made everyone go with us. We didn't go on the tour (reservations are recommended, but not really necessary in January) because I knew the youngest child wouldn't be willing to go, but we did watch the film at the visitor's center and walked around the outside of the house. I poked around the bookstore while everyone else played football behind the house.
It's a lovely place to stop, the film was good despite being a little old, and I'd recommend this one.
It's important to DC history because Frederick Douglass lived here from 1878 until his death in 1895. Neighborhood rules didn't allow blacks or Irish to own homes there so it's not known how he was able to buy the house. He had been appointed marshal for DC- the first time a black man received a Senate-approved federal appointment- but it was mostly a ceremonial role since he wasn't asked to fulfill many of the marshal's duties because he was black.
There's also a new Anacostia Heritage Trail that opened a few months ago that goes by Douglass' house.