She was the face of mass protest, but long ago lost her faith in protesting.

Then, last year, hundreds of thousands of women set out to march on Washington, and Jan Rose Kasmir knew she had to join them.

“When Trump was elected president, I couldn’t not participate. … It seemed like the only way to get my voice out there,” said Kasmir, 68, who was 17 when a photographer snapped a now-iconic image of her offering a chrysanthemum to National Guardsmen during a 1967 protest against the Vietnam War.

Kasmir gave up protesting when public opposition failed to stop the Iraq War in 2003. But after the 2017 Women’s March, she returned to the lines this spring to rally for gun control near her home in Hilton Head, South Carolina, joining a series of recent protests by millions of Americans demanding change.

“I think we’ve reached a tipping point,” Kasmir said.

There’s something happening here. But what is it, exactly, and why now?

More than five decades after Americans poured into the streets to demand civil rights and the end to a deeply unpopular war, thousands are embracing a culture of resistance unlike anything since.

In a country founded on the right to speak out against authority, every generation has hosted protests, from the watchfires set by women pushing for the power to vote a century ago to the Tea Party rallies shortly after the 2008 election. But the past year or two have seen a near-simultaneous explosion in activism around disparate causes.

NFL players have taken a knee during the national anthem. Teachers have packed statehouses to demand raises. Activists proclaiming “#MeToo,” have called out those who used their power to abuse them. High school students have walked out of classrooms nationwide to send an ultimatum to those who insist society needs more guns.

One of every five Americans has joined a protest or a political rally since the start of 2016, a recent poll by the Kaiser Family Foundation and The Washington Post found. Many more are Democrats than Republicans, with about a fifth telling pollsters they had never participated in a protest before.

Protests are “what America is all about. But this is bigger and more volatile” than in the recent past, said David S. Meyer, a professor at the University of California, Irvine and author of “The Politics of Protest: Social Movements in America.”

“We’re in a moment where people are frustrated with institutional politics and where people see urgent issues that need addressing and for a moment they believe that taking action can make a difference,” he said.

Opposition to Trump has clearly been a catalyst, he and others said.

For many activists on the left, “there’s a great deal of fear that we may be living in the last days of this experiment in democratic self-rule, that Donald Trump’s election may mark a fatal turning point,” said Maurice Isserman, a professor of history at Hamilton College and co-author of “America Divided: The Civil War of the 1960s.”

But experts on political activism say it is more complicated than that. Many of those protesting speak loudly for causes that go beyond electoral politics. And many of those concerns, like anger over shooting deaths or discrimination against African-Americans, predate Trump’s political rise by years. Much the same can be said of the turnout by white supremacists, at Charlottesville, Virginia, last spring and elsewhere, likely reflecting views held long before Trump’s election.

Such protests “didn’t spontaneously combust,” said Todd Gitlin, who in the early 1960s was president of the activist group Students for a Democratic Society and has gone on to study protest movements as a professor at Columbia University. “There are deep cleavages that are in play and they will manifest themselves in a variety of ways.”

The belief among an increasing number of Americans that their actions matter has drawn together broad coalitions — teens marching alongside senior citizens, whites agitating with blacks, native-born citizens gathered outside airport terminals with immigrants. Many speak of drawing power and inspiration from one another.

In Charlotte, North Carolina, Rachel Hewitt is back to protesting for the first time since the early 1980s, when she marched on the state Capitol as the General Assembly readied to vote down the Equal Rights Amendment. The catalyst this time was Trump, whose election left Hewitt deeply depressed.

So Hewitt, who is 65, white and works as a freelance graphic artist, boarded a bus, alone, to join the Women’s March. The shared sense of purpose she found among the huge crowds was “life-altering,” she said. After that, she was not one to go home quietly.

When students from south Florida’s Parkland High School organized the “March for Our Lives” last month in Washington, Hewitt chartered her own bus and filled it with 52 like-minded protesters, departing Charlotte at 11 p.m. the night before. The outpouring of youth she saw, both there and at events in Charlotte, introduced her to a new set of allies.

“It’s just thrilling to see that they very well could do what we weren’t able to do,” Hewitt said. She points to 16-year-old Amya Burse, who Hewitt connected with over their shared interest in gun control, and who began organized a safety task force and a rally at her Charlotte high school the day after the mass shooting at Parkland.

Burse said she has been jarred to action by her own experiences, most notably a lockdown last fall when a student brought a gun to school. But memes on social media have simultaneously alerted her to protests against domestic violence and other causes that demonstrate how many people are out there pushing their own version of change.

“When we started seeing one group getting enough success, we started realizing, well, maybe we can do something for myself,” said Burse, who is black and a junior. “Right now it feels like we’re in a miniature war, the fact that we can have so many movements just to make sure we’re safe.”

The prevalence of technology Burse talks about helps explain why protests have taken off, experts said. Even more so than just a few years ago, the widespread use of smartphones and the dexterity, particularly of young people, in using video and social media to shape their own message and connect with others have enabled them to organize quickly and effectively, Meyer said.

The resulting burst of activism may appear to be new. But it germinated for years before sparks like Trump’s election and the Parkland shooting set it off, said Christopher Schmidt, a professor at Chicago-Kent College of Law who has written about the civil rights activism of the 1960s and the rise of the Tea Party movement. The Occupy Wall Street protests in 2011 and the rise of the Black Lives Matter movement two years later pointed to deep restlessness on the U.S. political left, even as they raised consciousness on issues that continue to resonate, he said.

“It’s almost like the virus of social protest is moving throughout the social body,” said Micah White, one of the founders of the Occupy movement.

The recent wave of protests mark the first time since the 1960s that so many Americans have ventured into the streets. But students of that era, and those who participated in it, see at least many differences as similarities.

The ’60s were a hopeful and expansive time for many young activists, despite the polarization and anger that grew as the decade wore on, Isserman said, but today’s young protesters can’t afford such idealism.

“Today we have a harder sense of the limits and the choices that have to be made,” he said.

Schmidt draws parallels between the black college students who organized sit-in at white-owned lunch counters during the Civil Rights Era, and the Parkland students pushing for gun control. Both embrace the message of activists who have preceded them but reject the slowness or breadth of the results they have delivered. In doing so, today’s gun control activists have achieved an early measure of success merely by unsettling what most people regarded as the status quo, he said.

But the 1960s were a watershed because of the way its protests connected with one another over a sustained period of time to make significant changes in society, he said. It’s possible that, over time, protests like the Women’s March and #MeToo will lead to a lasting surge by women in voting and winning political office that will shift policy and behavior. But it’s far too soon to know whether today’s activism is truly transformative, or merely loud, analysts said.

“Everyone is so excited about the next social movement, but they have not solved the fundamental problem that large numbers of people in the streets does not lead to change,” said White, the Occupy co-founder.

Some of those who have taken to the streets share that uncertainty.

Johanna Goldfarb was a medical student in 1970 when the killing of four student protesters at Kent State University by National Guardsmen spurred her to join a rally against America’s war in Southeast Asia. She recalls how it made her feel proud to take a stand — and prouder, still, that activists of that era eventually made a difference.

Goldfarb, from the Cleveland suburb of Pepper Pike, said she joined the Women’s March last year more out of fear about the country’s direction than hope that she could change it. But when the recently retired pediatrician joined a march in downtown Cleveland to back the Parkland students’ demands for gun control, it reframed her mindset.

U.S. policies in Vietnam “changed because of what people did, because people spoke up. And I have to tell you, a recurrence of that feeling came as I watched the high school students. I thought, ‘Wow, these kids have energy. They know right from wrong and they know how to use the system.”

Perhaps, Goldfarb says, the strength of protesters’ number can yield lasting results. Maybe, individual Americans joined together, like those in the 1960s, are still capable of changing the country for the better.

“I’m being realistic,” she said. “I’m not sure that this is a movement. But I’m hopeful.”