From DC, started using there when swim was a teenager in the late 70s. #4 dillies off the street was the thing for white folks then, on corners that are now fully gentrified, but remembered fondly by us old hands. not old enough to recall the $1dope balloons, but all the users who showed me the ropes talked 'em up continually ...
Today swim is in the 'burbs and could get in and out of the DC corners easily. Know multiple delivery connects, etc. Do all swimming business in Baltimore, west side raw. You can get robbed or busted just as easily in either city, so driving an extra hour for high quality is what most everyone who has the option does. From Richmond, West Virginia, everywhere else, too.
Finding a smart street type and working up to meeting someone in a tourist area via a phone call is the eventual goal if swiy can afford it. Get a bundle or two, build some trust and rapport, talk to the guy who runs the courtyard or corner, swiy can get it set up pretty quick. Cops want us there to watch baseball or buy crab cakes, wont give any trouble at all and swiy can get back on the highway and out of town in a hot minute. Only reason to cop in DC is if you're a local street junkie without a car and two dollars short...
EDIT: BTW, if you are new and white in DC, it's pretty hard to figure out where to hook up. The 'ask a panhandler or hooker with big swollen hands' routine works anywhere, but more risky in DC than other places. The cops literally block off every entrance and exit to specific neighborhoods and won't let you in if you can't prove you live there or have legit business. Chief Lanier doesn't seem to care much about the constitution, so you can find out where those neighborhoods are by looking for Washington Post articles about how the ACLU is up in arms about whatever gestapo tactics they are currently using. But if you find out where to go via this method, you'll run into the gestapo sooner or later. It's not like it used to be, with what used to be some of the worst neighborhoods in the USA now yuppified and milk white and the classic dope corners with easy freeway access long gone.