Tens of thousands came to Washington, D.C., for the parade, which was meant to honor the 250th birthday of the U.S. Army, but also happened to fall on Trump's 79th birthday.

In a city notorious for unruly crowds at large sporting events, protesters were peaceful and law-abiding — as were the police.

Participants gathered at the Gateway Trailhead located at the railroad crossing before fanning out onto Main Street downtown.