Thousands of protesters from across the country — including some of the biggest names in the anti-vaccination movement — descended on the nation's capital Sunday for a rally against vaccine mandates.

Almost two years into a pandemic that has killed more than 860,000 Americans, the gathering on the Mall was a jarring spectacle: A crowd of demonstrators, many unmasked, decrying vaccine mandates in the middle of a city that has adopted mask and vaccine mandates to reduce sickness and death from the surge of the virus's omicron variant, which has battered D.C. for weeks.

Organizers had estimated that 20,000 people would attend the rally, marching from the Washington Monument to the Lincoln Memorial, according to a permit issued by the National Park Service. A smaller crowd of several thousand had arrived on the Mall by early Sunday afternoon.

Some were white-haired; others were being pushed in strollers. Most were White and many wore gear with slogans supporting former president Donald Trump. A group of men in front of a cart with a "Don't Tread On Me" flag started a chant of "Let's go Brandon" and "F — - Joe Biden" at around 10:30 a.m. to cheers. The few who wore masks risked the tirades of a man screaming "Take those masks off!" and "It's all a lie!"

Later about 10 men wearing the insignia of the Proud Boys, an extremist group involved in the Jan. 6 attack at the U.S. Capitol, lingered on the Lincoln side of the Reflecting Pool. They briefly engaged in a shouting match with a small group of counterprotesters at the edge of the rally, then walked away.

The marchers carried posters and flags that included false statements such as "Vaccines are mass kill bio weapons" and "Trump won." A bus was parked beside the Washington Monument, wrapped in signs with "ARREST OR EXILE" and displaying pictures of Anthony S. Fauci, Bill Gates and Jacob Rothschild — the last an echo of anti-Semitic conspiracy theories involving the Rothschild family. A speaker blared Kelly Clarkson's "Stronger (What doesn't kill you)."

Justin Perrault was demonstrating in D.C. for the first time. The 38-year-old from Fairhaven, Massachusets, said he had watched business to his body therapy and spiritual counseling business dry up as clients - afraid of catching the virus from an unvaccinated practitioner — stopped coming. He said he started using food stamps for the first time in his life, but was ashamed and worried what his children, ages 8 and 4, would think of him. He said he came to D.C. with his wife and her best friend not only to protest vaccination mandates, but also to take a stand against the scientific consensus that the vaccines are safe.

Jaedyn Wetzel, 12, stood nearby holding a sign that read "I have natural immunity." She said she was sickened with the coronavirus over Thanksgiving. She stood with her sister, Jessie, 14, and parents, who didn't want to be named for fear of discrimination based on the family's unvaccinated status. They drove to the District for the day from Warfordsburg, Pennsylvania, for their first protest in the nation's capital.

They said they haven't faced coronavirus vaccine mandates in their schools or workplaces, but wanted to protest because they are fearful mandates may be imminent. Their mother heard about the protest through Telegram channels, including one she said calls for auditing the Pennsylvania presidential election results, and doesn't like using Facebook or Twitter because she says those companies employ "censorship."

Police had a visible but not overwhelming presence on the Mall on Sunday, with about 10 mounted officers lining the march route and U.S. Park Police vehicles parked nearby. Officers were also at the Lincoln Memorial, where fences had been erected to prevent people from walking up the steps. A Metro police officer paced the area around the exit of the Smithsonian stop as march-goers carrying signs passed barefaced in violation of the transit system's mask mandate.

Metro officials said they are investigating an alleged assault Saturday night aboard a Red Line train in the District. In a Reddit post, the victim reported being attacked for wearing a mask by a man without a face covering.

Sherri L. Ly, a Metro spokeswoman, said the incident was reported to the Metro Transit police through an online harassment Internet portal. It was unclear if the victim is the one who reported the incident. "Investigators are reaching out to the victim and are investigating," Ly said. Attempts by the Washington Post to reach the victim were not successful.

D.C. police were fully activated from Friday Jan. 21, during the annual March for Life, through Sunday for the anti-vaccine mandate rally, spokesman Dustin Sternbeck said.

The march was billed as a protest of mandates, rather than the medicines themselves. But similar rhetoric — emphasizing individual autonomy rather than untenable scientific ideas — has long characterized the broader anti-vaccine movement, and the march's speakers included movement veterans such as Robert F. Kennedy Jr. and Del Bigtree, founder of the anti-vaccine group Informed Consent Action Network. The event was being live-streamed on the website of Bigtree's website, the High Wire, a which includes a prominent link that allows viewers to donate to ICAN.

Other speakers included physician Robert Malone, a critic of the coronavirus mRNA vaccines, and former CBS News correspondent Lara Logan, who in a November appearance on Fox News compared White House chief medical adviser Anthony S. Fauci to the Nazi doctor Josef Mengele. Public employee associations that have formed to protest their employers' vaccine mandates, such as Feds for Medical Freedom and D.C. Firefighters Bodily Autonomy Affirmation Group, also participated.

"The goal is to show a unified front of bringing people together — vaccinated, unvaccinated, Democrats, Republicans, all together in solidarity," said organizer Matt Tune, an unvaccinated 48-year-old from Chicago. He said he wants the event "to help change the current narrative … which is basically saying that we're a bunch of weirdos and freaks who don't care about humanity. And that's not true at all."

As speakers took to the stage — including a group of doctors in white physicians' coats — the crowd roared its approval at lines comparing vaccine mandates to the actions of authoritarian regimes such as Nazi Germany and the former Soviet Union and railing against the news media for its reporting on the scientific evidence supporting the coronavirus vaccines. (The Post, like many other large employers, requires its workers to be vaccinated against the virus.)

Two days after the Centers for Disease Control and Prevention released its first studies based on real-world data showing that the vaccines continue to provide strong protection against hospitalization from omicron, Malone stood on the steps of the Lincoln Memorial and falsely told thousands of cheering spectators that "the science is settled. They're not working."

Anti-vaccine activist Kevin Jenkins, who is Black, invoked the spirit of Martin Luther King Jr. as he stood on the same site where the civil rights legend delivered his best-known speech.

"The people in this crowd are on the right side of history," Jenkins declared.

Suzanne Robertson, 52, traveled from New Jersey for the anti-mandate march, carrying a sign that said she was a lifelong liberal Democrat until the last year. Robertson, who works in sales, said she contracted the coronavirus in March 2020 but only had mild symptoms. She said she campaigned for Bernie Sanders and voted for President Biden and had never before voted for a Republican until recently — when she stopped identifying with a political party all together, disappointed in Biden's chastisement of those who choose not to get the shot.

"This is not a political thing," Robertson said. "If you want to get the vaccine, get it."

Lindsay Mikus, 38, traveled from Westchester County, New York, to oppose the mandates. Her 14-year-old son lives with his father and is vaccinated, she said, but her 7-year-old daughter — whom she home-schools — is not.

"I have children and I believe they should live in a free country," Mikus said.

Mikus and Robertson said they are not vaccinated.

"I would die first," Robertson said.

An overwhelming body of evidence demonstrates that the coronavirus vaccines are safe and effective for most who receive them. As of October, according to the most recent estimates from the CDC, those who received two doses of the Pfizer-BioNTech or Moderna vaccines and a booster were 40 times less likely to die of the virus than the unvaccinated.

The CDC on Friday released studies showing that the vaccines continue to provide robust protection against hospitalization from the omicron variant, even if they no longer ward off infection as effectively.

Nevertheless, national surveys show about 1 in 5 U.S. adults remain unvaccinated. Among children ages 5 to 11, who became eligible for the shots in November, fewer than 20 percent are vaccinated.

The rally benefited extensively from publicity in recent weeks on prominent social media and podcasting platforms. Tune said the march's website saw a "huge spike" in traffic after Malone mentioned it on Joe Rogan's popular podcast, "The Joe Rogan Experience." Malone's appearance provoked a condemnatory letter to Spotify, which hosts the podcast, from hundreds of doctors and public health experts. Tucker Carlson also plugged the event during an interview with Malone.

More than 15,000 people joined a Facebook group for the rally, with many saying they would stay overnight and eat in Northern Virginia to avoid the District's vaccine mandate. Some commenters on the group's page have compared vaccine mandates to the Holocaust and urged people not to get tested for the virus.

Aaron Simpson, a spokesman for Meta, the parent company of Facebook, said that because the page is ostensibly opposed to vaccine mandates rather than vaccines it does not violate the platform's policies on COVID-19 and vaccine misinformation, which prohibit "content calling to action, advocating, or promoting that others not get the COVID-19 vaccine."

However, some individual posts and comments that contain misinformation have been removed, he said.

"Voicing opposition to government mandates is not against Meta's policies," Simpson said. "What we don't allow is content that promotes harmful false claims about the vaccines themselves and we remove those posts — including in this group."