Brooklyn College's campus was caked in snow, but people started filing in early in the day.
Attendees and volunteers made the best of the inclement weather, building a snowman in Sanders' honor.
As they waited for the man of the hour to arrive, attendees were entertained by a peace-preaching reggae band.
People danced and huddled together to keep warm.
Volunteers shoveled snow to clear space for the event.
People of all ages attended, but the crowd was primarily young and diverse.
Louis Nuñez, 43, of Brooklyn, stood out with his banana suit. He told INSIDER he's "bananas for Bernie." Nuñez said he's been a longtime Sanders supporter and wrote him in on the ballot in 2016.
George Shannon, 50, of the Bronx, told INSIDER he supports Sanders because "he's a true progressive" and he's the only "person running" for president who's "always been the same." Shannon, who volunteered at the event, said he disagrees with critics who say Sanders can't win over minority voters. "If you look at him for the last 20 years, he's been fighting for minorities," he said.
Nicole Rojas, 24, a recent graduate of Brooklyn College, told INSIDER she supports Sanders because he "understands" the immigrant experience due to his family history. The Vermont senator's father was a Polish immigrant, and many of his family members died in the Holocaust. Rojas, a volunteer at the event, comes from a mixed-status family from Mexico.
Jessie Rodriguez, 30, is originally from Bogota, Colombia. Rodriguez, who now lives in Brooklyn, told INSIDER she became a US citizen in September 2015 so she could vote for Sanders. "I believe in him more than anyone else," Rodriguez said, adding that as a "minority and a woman" she's proof Sanders appeals to a broad group of voters.
Patrizia Pelgrift, 48, who's originally from Milan, Italy, but has also lived in other European countries like the UK and Norway, said she supports Sanders because "he talks about politics I'm very familiar with." She and Rodriguez met while campaigning for Sanders in 2016. Pelgrift said she's married to an American doctor who supports Sanders' on Medicare for All.
Jane Sanders was the first speaker on Saturday. "I know it may not be politically correct to identify myself as a wife, but it's one of the great honors of my life," she said of her marriage to the Vermont Senator. Shortly before she left the stage, Sanders declared, "Today is only the beginning ... This is not a moment, it’s a movement!"
Nina Turner, president of Our Revolution and a co-chair on Sanders' campaign, got the crowd riled up touting Sanders' progressive record. "Brooklyn, you should be proud that the son of this city has been standing on the frontlines for a very long time — standing up for working people in this country," she said.
Shaun King, activist and journalist, was also among the speakers and touted Sanders' longtime efforts championing civil rights and working class issues. "It's his journey to this moment that makes me trust this man with our future," King told the crowd.
When Sen. Bernie Sanders finally came on the stage, the crowd exploded.
By the time Sanders began speaking, the venue was packed.
A Sanders campaign aide told INSIDER roughly 13,000 people attended the rally.
At one point during his speech, attendees began chanting, "Bernie, Bernie, Bernie," to which he replied, "No, no it is not 'Bernie' ― it is you." The crowd roared.
As Sanders spoke, people in the crowd held up posters that emphasized their support for him and the issues he's prioritizing as part of his 2020 platform.
Meanwhile, others wore pins to show their support.
A number of the posters seen at the event were overtly anti-Trump, which matched Sanders' rhetoric onstage.
During his speech, Sanders addressed an array of issues, touching on everything from climate change and campaign finance reform to mass incarceration and gun violence.
"Brothers and sisters, we are going to win this election ... because we are putting together the strongest grassroots campaign in the history of US politics," Sanders declared to a cheering audience.
A large portion of Sanders' speech focused on his Brooklyn roots and humble upbringing, which the Vermont senator contrasted with President Donald Trump's wealthy background. "I did not have a father who gave me millions of dollars to build luxury skyscrapers, casinos and country clubs ... But I had something more valuable: I had the role model of a father who had unbelievable courage in journeying across an ocean, with no money in his pocket, to start a new and better life," Sanders said.
As Sanders walked off the stage and the crowd dispersed, John Lennon's "Power to the People" blared on the speakers.