The Women's Marches may have been the largest demonstration in US history

http://www.vox.com/2017/1/22/14350808/womens-marches-largest-demonstration-us-history-map

"Crowd estimates from Women’s Marches on Saturday are still trickling in, but political scientists say they think we may have just witnessed the largest day of demonstrations in American history.

According to data collected by Erica Chenoweth at the University of Denver and Jeremy Pressman at the University of Connecticut, marches held in more than 500 US cities were attended by at least 3.3 million people.

Almost every state in America hosted a Women’s March, as you can see in the map above. The events ranged from tiny gatherings in small town squares to throngs of more than 500,000 people clogging streets in cities like Washington, DC and Los Angeles. (If you see that crowd attendance information is missing from your city, please contact the researchers here.)"