A 2017 march drew four million protesters, a US single-day record.

Evidence

On January 21, 2017, the day after Trump’s inauguration, signs emblazoned with the lyric “OK ladies, now let’s get in formation” appeared at the Women’s March, which drew four million people from across the United States—the nation’s largest-ever single-day protest at the time. Alongside the poptimist soundtrack, the event introduced a new cultural symbol: the pink, hand-crocheted “pussyhat,” with triangular corners resembling cat ears. — W. David Marx, Blank Space, 456