More properly it is part of "Prohibited Area P-56" on official maps. A second part of it is the Vice-president's residence at the Naval Observatory. there is an actually sign at the end of the runway at Reagan National Airport reminding pilots to avoid flying over P-56. DCA Reagan National - Aircraft ProceduresThe middle of the big red "NO FLY ZONE" circle on most aviation maps
You want the frequencies for the Washington SFRA as well as problably very close by Ronald Reagan National Airport. It is not really an area where Washington Center is controlling aircraft near the P-56. https://www.iflightplanner.com/Help/DC-SFRA-Filing.pdfI know it’s restricted, I was wondering what FREQ is used in that area, I’ve look at the sectional many times, maybe I’m overlooking it.