Mamdani, a Democrat, was sworn in at a decommissioned subway station below City Hall just after midnight, placing his hand on a Quran as he took his oath as the city’s first Muslim mayor.

After working part of the night in his new office, Mamdani returned to City Hall in a taxi cab around midday Thursday for a grander public inauguration where U.S. Sen. Bernie Sanders, one of the mayor’s political heroes, administered the oath for a second time.

“Beginning today, we will govern expansively and audaciously. We may not always succeed, but never will we be accused of lacking the courage to try,” Mamdani told a cheering crowd.

“To those who insist that the era of big government is over, hear me when I say this: No longer will City Hall hesitate to use its power to improve New Yorkers’ lives,” he said.

Throngs turned out in the frigid cold for an inauguration viewing party just south of City Hall on a stretch of Broadway known as the “Canyon of Heroes,” famous for its ticker-tape parades.

Mamdani wasted little time getting to work after the event.

He revoked multiple executive orders issued by the previous administration since Sept. 26, 2024, the date federal authorities announced former Mayor Eric Adams had been indicted on corruption charges, which were later dismissed following intervention by the Trump administration.

Then he visited an apartment building in Brooklyn to announce he is revitalizing a city office dedicated to protecting tenants and creating two task forces focused on housing construction.

‘I will govern as a democratic socialist’

Throughout the daytime ceremony, Mamdani and other speakers hit on the theme that carried him to victory in the election: Using government power to lift up the millions of people who struggle with the city’s high cost of living.

Mamdani peppered his remarks with references to those New Yorkers, citing workers in steel-toed boots, halal cart vendors “whose knees ache from working all day” and cooks “wielding a thousand spices.”

“I was elected as a democratic socialist and I will govern as a democratic socialist,” Mamdani said. “I will not abandon my principles for fear of being deemed ‘radical.’”

Before administering the oath, Sanders told the crowd that most of the things Mamdani wants to do — including raising taxes on the rich — aren’t radical at all.

“In the richest country in the history of the world, making sure that people can live in affordable housing is not radical,” he told the crowd. “It is the right and decent thing to do.”

Mamdani was accompanied on stage by his wife, Rama Duwaji. Adams was also in attendance, sitting near another former mayor, Bill de Blasio.

Actor Mandy Patinkin, who recently hosted Mamdani to celebrate Hannukah, sang “Over the Rainbow” with children from an elementary school chorus. The invocation was given by Imam Khalid Latif, the director of the Islamic Center of New York City. Poet Cornelius Eady read an original poem called “Proof.”

In addition to being the city’s first Muslim mayor, Mamdani is also its first of South Asian descent and the first to be born in Africa. At 34, Mamdani is also the city’s youngest mayor in generations.

Free child care and bus rides

At the watch party on Broadway, onlookers stood shoulder to shoulder gazing up at several jumbotrons and singing and dancing to stave off the cold, with some passing out hot cocoa and hand warmers. Many described feeling as though they were witnessing history.

Among them was Ariel Segura, a 16-year-old Bronx resident, who had arrived five hours earlier to secure a place near the front of the crowd.

“I’m out here fan-girling a politician, it’s kind of crazy,” he said, wiping away tears as Mamdani concluded his speech. “Now it’s time to hold him accountable.”

In a campaign that helped make “affordability” a buzzword across the political spectrum, Mamdani ran on a focused platform that included promises of free child care, free buses, a rent freeze for about 1 million households and a pilot of city-run grocery stores.

Mamdani insisted in his inaugural address that he will not squander his opportunity to implement those policies.

“A moment like this comes rarely. Seldom do we hold such an opportunity to transform and reinvent. Rarer still is it the people themselves whose hands are on the levers of change. And yet we know that too often in our past, moments of great possibility have been promptly surrendered to small imagination and smaller ambition,” he said.

But he will also have to face the everyday responsibilities of running America’s largest city: handling trash and snow and rats, while getting blamed for subway delays and potholes.

In his speech, Mamdani acknowledged the task ahead, saying he knows many will be watching to see whether he can succeed.

“They want to know if the left can govern. They want to know if the struggles that afflict them can be solved. They want to know if it is right to hope again,” he said. “So, standing together with the wind of purpose at our backs, we will do something that New Yorkers do better than anyone else: We will set an example for the world.”

Quick rise to power

Mamdani was born in Kampala, Uganda, the son of filmmaker Mira Nair and Mahmood Mamdani, an academic and author. His family moved to New York City when he was 7, with Mamdani growing up in a post-9/11 city where Muslims didn’t always feel welcome. He became an American citizen in 2018.

He worked on political campaigns for Democratic candidates in the city before he sought public office himself, winning a state Assembly seat in 2020 to represent a section of Queens.

Now that he has taken office, Mamdani and his wife will depart their one-bedroom, rent stabilized apartment in the outer-borough to take up residence in the stately mayoral residence in Manhattan.

The new mayor inherits a city on the upswing, after years of slow recovery from the COVID-19 pandemic. Violent crime has dropped to pre-pandemic lows. Tourists are back. Unemployment, which soared during the pandemic years, is also back to pre-COVID levels.

Yet deep concerns remain about high prices and rising rents.

In opening remarks to the crowd, U.S. Rep. Alexandria Ocasio-Cortez praised New Yorkers for choosing “courage over fear.”

“We have chosen prosperity for the many over spoils for the few,” she said.

Dealing with Trump

During the mayoral race, President Donald Trump threatened to withhold federal funding from the city if Mamdani won and mused about sending National Guard troops to the city.

But Trump surprised supporters and foes alike by inviting the Democrat to the White House for what ended up being a cordial meeting in November.

“I want him to do a great job and will help him do a great job,” Trump said.

Still, tensions between the two leaders are almost certain to resurface, given their deep policy disagreements, particularly over immigration.

Several speakers at Thursday’s inauguration criticized the Trump administration’s move to deport more immigrants and expressed hope that Mamdani’s City Hall would be an ally to those the president has targeted.

Mamdani also faces skepticism and opposition from some members of the city’s Jewish community over his criticisms of Israel’s government.

Still, Mamdani supporters in Thursday’s crowd expressed optimism he’d be a unifying force.

“There are moments where everyone in New York comes together, like when the Mets won the World Series in ’86,” said Mary Hammann, 64, a musician with the Metropolitan Opera. “This feels like that — just colder.”

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Associated Press writer Jake Offenhartz contributed to this story.