They were teachers and lawyers, military veterans and fired government employees. Children and grandmothers, students and retirees.

Arriving in droves across the country in major cities and small towns, they appeared in costumes, blared music, brandished signs, hoisted American flags and cheered at the honks of passing cars.

The vibe in most places was irreverent but peaceful and family-friendly. The purpose, however, was focused. Each crowd, everywhere, shared the same mantra: No kings.

Collectively, the daylong mass demonstration against the Trump administration on Saturday, held in thousands of locations, condemned a president that the protesters view as acting like a monarch.

Many had attended a similar event in June, but the months since had seen President Trump make a dizzying array of changes in quick succession.

This time, the crowds included a new round of protesters, those who said they were outraged over immigration raids, the deployment of federal troops in cities, government layoffs, steep budget cuts, the chipping away of voting rights, the rollback of vaccine requirements, the reversal on treaties with tribes and the so-called One Big Beautiful Bill.

Despite heavy rain, protesters turned out for the ‘No Kings’ demonstration in Dallas on Saturday. Credit…Desiree Rios for The New York Times

Many were also united in saying the administration needed to show basic humanity.

“We can argue and debate policies and ways that we can solve problems,” said Chris Scharman, a lawyer who attended a rally in Salt Lake City. “But we shouldn’t be debating the value of people.”

In major metropolitan areas, like Washington, D.C., the crowds were huge. A rally in Atlanta that drew thousands at one point covered three city blocks. A protest in San Francisco poured across five. One rally in Chicago stretched over 22.

Officials in New York said that more than 100,000 people demonstrated across all five boroughs of the city. One of the largest turnouts was in Times Square, where the streets were awash in a carnival-like atmosphere with flashy, flippant signs, one that announced “I Pledge Allegiance to No King.” Protesters sported the inflatable frog ensemble that activists in Portland, Ore., began wearing to poke fun at the White House’s attempt to portray activists as anarchists or domestic terrorists.

“No more Trump!” the crowd chanted as they waved American flags.

VideoLarge Protests Flood Streets to Denounce TrumpKnown as No Kings Day, the demonstrations built off a similar event in June.CreditCredit…Jon Cherry for The New York Times

“We’ve got to speak up for our rights, especially if we’re lucky enough to be citizens,” said Bianca Diaz whose 6-year-old daughter, Luna, came dressed as an axolotl, a kind of salamander. “I wanted her to witness this,” Ms. Diaz said.

Known as No Kings Day, a follow-up to a demonstration in June, the events were scheduled at roughly 2,600 sites across all 50 states. They were organized by national and local groups and well-known progressive coalitions including Indivisible, 50501 and MoveOn.

The rallies came even as Mr. Trump’s approval ratings at the polls have not changed significantly. Republican leaders denounced the protests, blaming them for prolonging the government shutdown and calling the event the “hate America rally.”

Mr. Trump’s political team trolled protesters on social media with AI-generated images of the president wearing a crown. When asked if the president had a comment on the demonstrations, Abigail Jackson, a White House spokeswoman, gave a brief response in an email.

“Who cares?” she said.

The march in Chicago stretched over 22 blocks at one point.Credit…Jamie Kelter Davis for The New York Times

Ms. Diaz, 39, was one of those who did. She said she heard about the demonstration on TikTok and knew immediately that she would attend. A claims adjuster employed by the federal government, she has not been paid since the shutdown but said she supported the position of Democratic politicians who were pushing to keep health care costs down. A mass protest, she said, could be encouraging to leaders pursuing that goal.

“Protesting is the only way to get our voices out,” said Libby Smith, 17, who attended a rally in Pittsburgh. She said her plans to join the military after high school were deflated when Pete Hegseth, the defense secretary, fired a string of women leaders and said he wanted women out of combat roles.

Some 400 miles southwest in Richmond, Ky., where President Trump has handily won the past three general elections, protesters lined the sidewalk outside the local courthouse. A few drivers in passing cars jeered and shouted pro-Trump declarations, but others appeared to honk in support.

Protesters gathered on the steps of the Idaho State Capitol in Boise on Saturday.Credit…Loren Elliott for The New York Times

“This is what democracy looks like!” protesters chanted, led by a woman with a megaphone. “No kings, no kings, no kings in America!”

Protesters in Portland, Ore., where city and state leaders were fighting the president in court over his plans to deploy the National Guard there to address what he said was violence that was out of control, took part in three separate marches that eventually coalesced into one.

“We are out today to show people that this is not a war zone,” said Shawnathan Thibodeaux, 37, a middle school history teacher who attended with his wife and 4-year-old son. “The ultimate goal of describing this city that way is terrifying. We are peaceful and silly and still Portland.”

Around the country, strangers met and swapped their long lists of grievances with one another: the government shutdown, the tariffs, Mr. Trump’s attacks on higher education, the pressure he has placed on the Justice Department to prosecute political enemies, the erosion of women’s rights, and the disbanding of D.E.I. programs.

Although some rallies saw small groups of counterprotesters and a police presence, the mood at most was upbeat and festive. At a demonstration in Washington, children and families were prominent. (Hours after a large rally ended in Los Angeles, about 100 protesters occupied an intersection before police officers in riot gear dispersed the crowd, the police said.)

In San Francisco, a crowd surrounded by farmers market vendors chanted, “Keep calm, keep marching!” At Grant Park in Chicago, thousands of attendees roared in applause as speakers took to the stage, including Illinois governor JB Pritzker, who urged demonstrators to reject the idea of a government with unlimited power.

People wrote messages on a banner of the preamble of the Constitution outside of the Department of Labor in Washington.Credit…Jason Andrew for The New York Times

Marilyn Ricken, 80, was in the crowd, having arrived with three friends, two of whom relied on walkers to move around.

Ms. Ricken, a retired insurance agent, had been at the No Kings rally in June but said Saturday’s event came with a deeper sense of urgency. “This is how change happens,” she said as nearby protesters signed their names at the bottom of a large replica of the U.S. Constitution.

In a show of solidarity, protesters around the world held demonstrations outside U.S. embassies, consulates or at town squares, including in Prague, Vienna and Malmo, Sweden.

In Paris, protesters raised placards denouncing Mr. Trump. In Germany, rallies were planned in four different cities, including one outside the Brandenburg Gate in Berlin. In countries with long-established monarchies, like Britain and Spain, protesters gathered under the slogan “No Tyrants.” In San Miguel de Allende, Mexico, many carried colorful signs rebuking ICE.

The forcefulness of Mr. Trump’s second term may have galvanized protesters, said Jeremy Pressman, a political science professor who co-directs the Crowd Counting Consortium, a joint project of the Harvard Kennedy School and the University of Connecticut.

“The intensity of the action is going to feed into the intensity of the counteraction or counterprotest,” he said.

Many protesters said they were heartened by meeting peers.

“You feel like your voice isn’t that loud,” said Michael Flanagan, 46, a medical administrator who attended a rally in Memphis, where the National Guard was recently deployed. “But I’ve never seen this level of enthusiasm.”

A crowd marching through downtown Portland, Ore.Credit…Jordan Gale for The New York Times

In Manhattan, two siblings, Joyce Pavento, 75, of Marlborough, Mass., and Diane Hanson, 78, of Narragansett, R.I., were similarly encouraged, to a degree. They had felt compelled to travel to New York City for the protest.

Ms. Pavento said she enjoyed the camaraderie of like-minded people but wondered if their participation made any difference in the end.

Yet despite pessimism and fears, the sisters agreed they couldn’t tolerate staying home.

“What choice do we have?” Ms. Pavento asked.

“This is all we’ve got,” Ms. Hanson said.

Reporting was contributed by Pranav Baskar from New York; Robert Chiarito and Leigh Giangreco from Chicago; Lynsey Chutel from London; Miles Cohen from Newark, N.J.; Sheryl Gay Stolberg from Shepherdstown, W.Va., Tricia Fulks Kelley from Richmond, Ky.; Matt Furber from Boise, Idaho; Anna Griffin from Portland, Ore.; Sean Keenan from Atlanta; Coral Murphy Marcos from San Francisco; Orlando Mayorquín from Los Angeles; Tyler Pager and Darren Sands from Washington; Nate Schweber from Manhattan; Katharine Q. Seelye from Philadelphia; Ben Stanley from Memphis; Makaelah Walters from Brooklyn; Aaron West in Salem, Ore.; Billy Witz in Pittsburgh and Benjamin Wood from Salt Lake City.