After reading your thread last night, I got to thinking what a great "if I had a million" layout the Eckington/Ivy City/Trinidad area could be. What newcomers see as FedEx and new housing on theNorth side of NY & FL now were once expansive freight yards with many large warehouses. Eckington probably dispatched at least 5 locals a day to work D.C., up the Met, and over to Georgetown. I don't think there's a single freight customer served by CSX any more. Then move down to Ivy City where you had the roundhouse taking care of all the locomotives from different railroads serving the city. Now throw in Washington Terminal and all the work they did at Union Station as well as everything the Pennsylvania/Penn Central did...a lot of action for a small area back then but unless it's Amtrak or the commuter lines, trains hardly tap the brakes going through D.C. these days...
For a good historical perspective, check out Bruce Elliott's B & O photo CD's, he's usually at Timonium with the B & O Historical Society guys; if not
www.rrslidesbybruce.webs.com one of his CD's has a number of shots of the area.