Yeah, we kind of figured they just started marching early because of the size of the crowd at the Plaza had grown too large. We joined in at about the Federal Triangle area around 10:20 and by that time it was obvious the march had been going on for some time. We saw nothing but people in front of us (and behind us) nearly all the way to the Capitol, so they must have started much, much earlier than anticipated.
Glad you were there.
Was one of the best days of my life.