Saturday’s nationwide March for Our Lives protests saw thousands of young Americans take to the streets to demand change — and the day of action is inspiring them to head to the polls.

The March for Our Lives organizers partnered with nonprofit organization HeadCount to register voters during the marches, with HeadCount deploying hundreds of volunteers to 30 of the marches, including those in New York City and Washington. As a result of its efforts, HeadCount founder Andy Bernstein said in an interview Sunday that the organization, which typically registers voters at music events, had the biggest day of voter registrations in its 15-year history.

“This was the No. 1 day in our history, by a wide margin. Nothing else was even close,” Bernstein said.

As of Saturday evening, Bernstein said his organization had counted over 4,000 registration forms, including 757 from the New York City march and over 1,500 from Washington. That total is expected to climb, as the organization was still waiting to count registration forms from eight to 10 of the marches where it had a presence.

“I really can’t describe how special it was. I’ve been on the phone all day with people around the country who were part of it, and everyone is feeling like they were really part of something historic,” Bernstein said. “It just all worked; it all came together. It brought people together around this higher goal of registering voters.”

“Everywhere you looked, everywhere you were at a march, you’d see somebody registering voters, and we achieved that,” Bernstein added. “It was a saturation, and that was what we set out to do.”

The recent shooting at Marjory Stoneman Douglas High School in Parkland, Florida, and the student-led political activism it inspired has sparked a wave of enthusiasm for voter registration, as the movement’s young leaders have emphasized the importance of voting to enact change.

“With this movement, we will ensure record-breaking turnout not just in the next presidential election, not in the next midterm election, but in all elections,” Stoneman Douglas student Sari Kaufman told a crowd at a Saturday rally in Parkland, according to Reuters. “We’re here today to give you the tools to make a change.”

In the days after the shooting, Stoneman Douglas student Emma Gonzalez ended a speech with a call for those who support her message to register to vote, which Bernstein cited as a major inspiration for Saturday’s voter registration wave.

“When Emma Gonzalez gave her speech and ended it with ‘the thing we all need to do is register to vote,’ she threw a pebble in the water that is rippling into a tidal wave,” Bernstein said.

Other organizations were out registering voters at Saturday’s rallies in addition to HeadCount, including the Palm Beach Indivisibles and Forward Alabama. Diane Burrows, a vice president at the League of Women Voters, told NBC News that the organization had “probably registered hundreds” of voters during Saturday’s rally in New York City.

“The engagement has really increased and I think it’s an awareness,” Burrows said. “People are really understanding the power of the vote and that’s what’s really motivating a lot of them. They’re figuring out the importance and power of civic engagement.”

Palm Beach Indivisibles volunteer Pam Weisbrod told BuzzFeed News that the response at a Florida rally to the organization’s efforts had been “amazing.”

“I’m encouraged by what I’m seeing today,” Weisbrod said. “I think this will be one of the bigger turnouts for the midterms.”

With the November midterm elections approaching, Saturday’s surge of voter registrations is just one part of a broader movement to inspire more young people to vote. Americans ages 18-29 have made up only 12-13% of the total electorate in the past six midterm elections, the Guardian reported in 2014, and 50% of eligible people between 18 and 29 voted in the 2016 presidential election.

“We registered a ton of voters yesterday, but this is just the beginning,” Bernstein said. “You can’t really measure this by how many voters we registered yesterday — what you measure it by is what kind of momentum this creates between now and the midterm elections and also leading up to 2020.”

Bernstein said he hopes to harness the team of 2,000 volunteers that HeadCount assembled for Saturday’s marches, many of whom were volunteering with the organization for the first time, for future efforts.

“We gathered this army of people who were motivated by the cause, inspired by the Parkland students, and now are ready for more,” Bernstein said. “And that’s a really big deal, and that’s how movement-building works.”

HeadCount will also build on the March for our Lives momentum through new initiatives, Bernstein said, such as a guidebook for students and teachers explaining how to register young Americans in schools. Bernstein says he hopes their efforts will inspire more high schools to make voter registration available to their students, with an ultimate goal of having 90% of American high schools providing voter registration by June.

“We definitely think there’s a possibility for setting off a movement, post-March for Our Lives, where if a school isn’t doing voter registration, they’re going to have to explain why,” Bernstein said. “So that’s how we turn the 4,000 voters we registered yesterday into a movement to register 4 million. There are 4 million newly eligible registered voters turning 18 this year, and there’s absolutely no reason that all of them can’t have an opportunity to register to vote easily.

“It’s all about movement-building; it’s all about identifying the people who are going to make these things happen, and what started with Emma Gonzalez. By June of this year, I am absolutely certain that we are going to have a game-change in this country,” Bernstein continued.

“Typically less than half of 18-year-olds are registered, and we are going to change that up this year. And it’s because of this movement, and it’s because of March for Our Lives, and it’s because of having networks of people all over the country who are committed to this kind of thing.”