ptownrob, while you suggest "no one seems to be able to cite the university" who gave the estimate, cursory research suggests differently. That would be the University of Illinois, according to Beck, that made the estimate. You must have missed it. Take your pick from the link below that includes Beck's representation that U. of Illinois did a crowd estimate. It would appear the source, one that you may suggest is bias, gives a fairly objective assessment of the issue.

From my experience, your own estimate is fairly accurate although I would lean more toward the high side of center you suggest.

Thank you for acknowledging that the rally and march actually took place.

http://74.125.47.132/search?q=cache:...&ct=clnk&gl=us