“This is truly an honor and a privilege of a lifetime,” Mamdani said. “And after just having taken my oath to become the mayor of the city of New York, I do so also here in the old City Hall subway station, a testament to the importance of public transit to the vitality and the health and the legacy of our city.”

The moment caps an extraordinary year in New York City politics, and one few expected would end with Mamdani walking into City Hall following the midnight ceremony to take control of the nation’s largest city. The democratic socialist campaigned on an ambitious, costly agenda that included universal free child care and free buses, paid for in part by hiking taxes on the wealthy and corporations.

Now-former Mayor Eric Adams incinerated his prospects to win a second term on a pyre of corruption from his inner circle and salvation from President Donald Trump. That allowed Mamdani to mount a historic campaign focused on affordability that energized young voters and triumphed over former Gov. Andrew Cuomo, who had sought a comeback as a moderate Democrat after resigning from office in 2021 amid sexual harassment allegations he has long denied.

Mamdani now takes the helm of a workforce topping 300,000 and faces pressing challenges in the form of budget negotiations, politicking in the state Capitol for his major proposals and the ever-present threat of federal immigration enforcement from Washington.

The new mayor has been filling out his cabinet, and took the opportunity during his swearing in to name the new head of the city’s Department of Transportation, Michael Flynn, who spent the prior two decades in various roles at New York state’s transportation agency.