Ah thank you Minus, I see that according to the data you posted (here’s your link again http://www.flickr.com/photos/njpitney/5045134373/meta/) the picture was taken at 12:04PM EDT. I am having a bit of trouble finding the schedule to determine peak attendance.
This blogger posted “15 Photos you won’t see in the legacy media” which mainly focused on large banners promoting socialism and pics of books for sale running the socialist/Marxist gamut: http://directorblue.blogspot.com/2010/10/15-photos-from-onenation-rally-youll.html
Oh I see that the OneNation organizers claim, on their ‘org’ page that 175 thousand people attended - more than they ever dreamed!