As recently as April 7, 2007, it snowed about an inch in D.C., but 0.4" was the official measurement at DCA. Here's a shot I took that day at the Capitol.
A bumper of a F-150 is not a great snowboard, but it provided the deepest snow measurement. The average measurement was 3.2" near Oakton, Va. That last snow burst was impressive.
This has become one of my favorite photos of Snowmageddon. It shows the depth and density of the snow. You'll never see this kind of photo with lake-effect snow.