When DCA operates in North Flow, aircraft are queued to make the final approach over the river from Piscataway Creek to Runway 1/19. Aircraft approaching from the south can simply get in line further south of Accokeek; aircraft approaching from the east or west meet a parallel path to the approach heading south before making a 180 degree turn onto the approach. This path and turn is known as a "Trombone Maneuver".
As the airport gets busier and more planes are queued up for landing, the trombone arm (and the turn) will get pushed south; so, while early in the morning they may have been turning over Piscataway Park or even further north, during peak periods they may be turning over Waldorf and La Plata.
A few screenshots from webtrak will illustrate this:
6:30 AM. Relatively few aircraft in operation. Because the queue is short, the turn is made north of the bend in the river. (Incidentally, because of the Nighttime Noise Rule, these aircraft would be fined by MWAA if they are noncompliant in terms of type of engine, i.e. cause too much noise; only 1% of aircraft using the airport currently fall into this category.)
6:50 AM. Now a wide swathe of Accokeek starts to get flyovers, as aircraft from both east and west make the turn directly overhead.
7:30 AM. The trombone arm has moved south of 210.
10:35 AM. One of the operations peaks on this particular day. The trombone arm has moved as far south as La Plata.
The "arm" moves back and forth all day. If your house is under the central approach path, you will have traffic passing over you all day during North Flow operations. If your house is between the parallel paths and the approach path, you'll have air traffic passing over your house during the 180 degree turn when the trombone is at your latitude. (Now you can impress your visitors with your knowledge of how busy the airport is based on where aircraft are turning relative to you.)
Southern Maryland Fair Skies Coalition doesn't believe that this distribution is fair, particularly for those who live under the main paths. We agree with the MWAA that planes should fly over water more than over land, and are advocating for a revision to this pattern accordingly. We seek volunteers to help us with this effort.