The DC authorities don't give an official estimate of any crowd, and few media outlets are willing to go out on a limb on their own. Crowd estimates never make anyone happy, and rarely make anyone happy.
They regularly publish the organizers’ estimates, with a disclaimer that it’s unofficial. At least when the organizer is an anti-war outfit like A.N.S.W.E.R.
Several RTL groups estimated the attendance to be around 200,000. Their estimates didn’t get a mention anywhere in the mainstream press.