Transcript for Trump's First Day in Office Met by Demonstrations in Multiple Cities Around the US
President Donald Trump's first full day in office, met by one of the largest inauguration-related demonstrations in U.S. History. A sea of protesters, mostly women, marching on Washington today. Organizers and other officials claiming big turnout. And not just here in the nation's capital. Millions marched in cities around the country, from los Angeles to St. Louis, Chicago to Boston. And take a look at the map. Those protests dotting the nation. An estimated 670 events taking place worldwide. This woman right here echoing today's themes of solidarity and defiance. Her sign, "Tweet women with respect." ABC's Matt Gutman has been following the movement all day, and he starts us off. Reporter: Tonight, that boisterous condemnation of president Donald Trump, filling the site of Friday's inauguration with a sea of pink beanies. Officials estimate about 500,000 demonstrators, but organizers believe 750,000 crammed into the city. The presidential motorcade passing right by some of those protesters. This was the view from the press pool. That massive demonstration anchored by the kind of a-list celebrities that snubbed president trump. Welcome to the revolution of love! Reporter: But those thousands bearing placards with individual messages like "Girls just Wann have fundamental rights." And "Strong women equals strong world." Streams of humanity are converging on this sea of people wearing pink beanies, all of them moving towards the white house. Scenes like the March in Washington repeated across the country. Demonstrators coming out by the thousands. Everyone is welcome here! Reporter: ABC's Mara schiavocampo at one of the biggt rallies, in New York. Here in trump's hometown, organizers say the crowds are exceeding the 150,000 people expected. The turnout so large, the city has to open up additional streets. Here for women's rights. Here we are in Tucson at the women's March. There's over 5,000 people here. We're all fighting for the same thing. Equality. Reporter: From Melbourne Australia to Denver. From Pittsburgh, all the way to about abilis anarctica. But so many of those protesters coming from all around, just to March here in Washington. By plane. And trains. Been on this train for about four and a half hours now. Reporter: And buses. Like this group, calling itself the faithful nine, among 54 people to board this bus from a speck of a town in the rust belt called yellow springs, Ohio. Julia badly injured her ankle earlier in the week, so, the community pitched her in to get her here. Even with that wheelchair. So, we wouldn't be here without a lot of the women that weren't able to go, that donated tickets and things to us, as well. Reporter: Wow. The faces in this massive crowd, old and very young. You know you have the best seat in the house right now. And Matt joins us now live from the scene of today's March. There were so many people out there, it took them a lot longer than expected to get to the white house, Matt? Reporter: That's right. There were so many people, those crowds so thick, that formal organization essentially broke down. So, folks were told to make their way to the white house any way they could. They ultimately nearly surrounded it, but Donald Trump wasn't in for most of the day. Still, they sent a message that was impossible not to hear. Cecilia? A loud message, indeed. Matt, thank you.
This transcript has been automatically generated and may not be 100% accurate.