My apartment faces generally North/Northwest. I routinely see helicopters flying NE to NW and vice versa (mostly medical "lifeflight" type).
I see Bell-looking copters (Park Service, DC PD) flying over the NW area (Dupont Ciircle area) all the time.
Over Naval Observatory, see Presidential marked copters flying from way-upper NW (Bethesda/Chevy Chase Area) down towards Observatory then frther south over the GW/Foggy Bottom area towards the Potomac.
Finally, up and down the Potomac - Bell-looking, plus others (possibly military and Marine/Presidential-marked) heading around.
In short, just about everywhere. They're like sirens in DC, common, everywhere, you don't even notice 'em.