A crowd-size expert from the U.K. estimates that between 10,000 to 15,000 people attended Saturday's protest in downtown Chicago. But some estimates say 75,000 people gathered downtown.

Across the country, an estimated 5 million protesters took part in more than 2,000 protests, according to the American Civil Liberties Union, a co-sponsor of the nationwide protest. In the Bay Area, more than 50 protests were planned stretching south from Gilroy north to Santa Rosa.