However, the 12,000-person event was different than his other large rallies.
Sanders and the lawmakers who introduced him mentioned racial inequalities throughout the event, a nod to the Black Lives Matter movement and the Vermont senator's earlier speech in Seattle that was shut down by protesters.
"Brothers and sisters, what a turnout," Sanders said at the start of his speech. "It doesn't seem true but we began this campaign about three and a half months ago, and the momentum has been unbelievable."
The latest turnout, which was verified by arena staff, supersedes the more than 11,000 people who attended a Sanders rally in Phoenix in July. Doors were closed at the venue, according to arena staff, before the rally started. Sanders' campaign said the candidate also spoke to around 3,000 people outside the venue who were not able to get inside.
The energized audience, many of whom lined up hours before the event, cheered at nearly everything he said. Sanders, his shirt soaked with sweat, said the turnout proved that "people are tired of establishment politics, establishment economics and they want real change."
The atmosphere was markedly different than Sanders' first event of the day, where Black Lives Matter protesters confronted the senator
and shut down his event.
Though he did not directly address the earlier disturbance, Sanders cast himself as a lifelong fighter for civil rights.
"No President," he said, "will fight harder to end the stain of racism in this country and reform our criminal justice system. Period."
Later in the speech, Sanders touched on an issue Black Lives Matter protesters want to hear more on.
"It makes more sense to me to be investing in jobs and education for our kids than in jails and incarceration," he said.
Sanders was introduced by a series of speakers, nearly all of whom mentioned Black Lives Matters.
"Sen. Sanders knows, as do I, that Black Lives Matter," state Rep. Luis Moscoso said. "Racial inequality is as serious as economic inequality. No one should be dehumanized by their race."
State Sen. Pramila Jayapal said Sanders knows "it is not enough just to say we care, it is not enough. What we have to do is call out personal, individual and institutionalized racism at every opportunity."
Sanders' campaign also announced Saturday that Symone D. Sanders, an African-American woman, has been hired as its national press secretary.
Sanders serves as the national youth chair of the Coalition on Juvenile Justice.
The new press secretary introduced Sanders with a 10-minute speech on racial tensions and named the African-American men and women who have died at the hands of law enforcement.
"You know which candidate for President will shut down the private prison industry," she said to roaring applause. "You know which candidate will have the courage to fight unjust mandatory minimums and the death penalty."
Symone Sanders said her job with the campaign started Saturday, but the process of getting hired started three weeks ago with an hour and a half long meeting with the senator. She said one of the reasons she joined the campaign was because of the senator's willingness to listen to suggestions on race issues.
"I wanted to see just who Senator Sanders is, how he thought and how open he was to talking about his actual message and how open he was to suggestions," she said. "He is super flexible, he is cool and he has a great heart."
Sanders has been dogged by Black Lives Matters protesters since July. They interrupted his speech to Netroots Nation, a liberal conference, and have routinely called on him to address police reform.
Symone Sanders said the campaign would be putting out a detailed plan on the issue soon, but would not give a timeline. She said one key to winning support from the African-American community will be educating people on "who Bernie Sanders is."
"It's not just about, I fought for civil rights and I protested and I sat at the lunch counters," Symone Sanders said, parroting a line the senator regularly uses on the stump. "That is important and that is great, but that was 50 years ago. And he has a lot more to stand on than what he did 50 years ago."
The newly minted national press secretary appeared confident that protests at Sanders' events would quell once more people learned about the senator.
"I think some people haven't heard it yet," she said. "They haven't received it yet. But I think they will hear it and they will receive it."
Though he serves as an Independent in the Senate, he is a Democratic candidate for President.