This morning, I posted a third map, this one showing the Potomac River
area where Hwy 66 enters the District, but which also shows a number
of other roads that "dip" in and out of the District on the VA side of
the border. It's a large, detailed map, and you will see a section of
the shore west of Roosevelt Island but on the east edge of 66 as it
turns south along the river. The shore at this location dips under
the roadway for 50 feet or so, meaning that the road hangs over into
the District airspace at this point. I'll try to take and post a
photo of this areas and to get a more precise length. In any case it
is shorter than the width of the Wilson Bridge portion that goes
through the southern "pie slice" of DC. Study the map a little -
maybe you can spot other areas where these roads ignore the borders.

LN