Our estimate is based on reports from local officials, local organizers, and attendees, and suggests the count from organizers — who report 7 million participants nationwide — may be a bit optimistic (but is not impossible). Still, regardless of whether the precise number is 5, 6, 7, or 8 million, Saturday’s events are very likely the biggest single-day protest event since 1970, surpassing even the 2017 Women’s March demonstrations against Trump.