The thing I liked best about the ceremony? The inclusion of Dasani Coates, the ambitious homeless girl recently profiled in the New York Times, in the festivities. What a change from Bloomberg! I wish Mayor DeBlasio the best in the enormous task of making one city out of two:

Bill de Blasio claimed his place as the 109th mayor of New York City shortly after 1 p.m. on Wednesday, delivering an inaugural address at City Hall in front of luminaries like Bill and Hillary Rodham Clinton as well as hundreds of ordinary New Yorkers.

“We are called to put an end to economic and social inequalities that threaten to unravel the city we love,” Mr. de Blasio said. “And so today, we commit to a new progressive direction in New York. And that same progressive impulse has written our city’s history. It’s in our DNA.”

Mr. de Blasio, 52, was formally sworn in shortly after midnight in a brief ceremony in front of his family’s rowhouse in Park Slope, Brooklyn. On the steps of City Hall, he was ceremonially sworn in by former President Clinton, in whose administration he served as a regional official in the Department of Housing and Urban Development. Mr. de Blasio was sworn in using a Bible once owned by Franklin Delano Roosevelt.

“There are some who think that now, as we turn to governing – well, that things will just continue pretty much like they always have,” Mr. de Blasio said. “So let me be clear: When I said I would take dead aim at the tale of two cities, I meant it. And we will do it.”

A Democrat, the new mayor begins his term as an emblem of resurgent liberalism, offering hope to progressive activists and officeholders across the country — but also as an untested chief executive whose management of the city will be closely scrutinized.

Previously the city’s public advocate and before that a city councilman, Mr. de Blasio rose out of obscurity in a crowded Democratic primary field as he shaped his campaign around the “tale of two cities” — a succinct summation of the rising income inequality he vowed he would urgently address as the next mayor.

He won a landslide victory on Nov. 5 over the Republican candidate, Joseph J. Lhota, seizing on an anxiety among voters that the city was increasingly becoming a gilded enclave for the rich, and vowing a sharp turn from the administration of his predecessor, Michael R. Bloomberg who served for 12 years.

Mr. de Blasio appeared at City Hall on Wednesday with his wife, Chirlane McCray; his 19-year-old daughter, Chiara; and his 16-year-old son, Dante.

Mr. de Blasio’s inauguration team last week made 1,000 tickets available to the public. They were claimed within two hours.

Dozens of other New Yorkers were invited to join Mr. de Blasio on stage at the event, including an engineer from Queens who emigrated from Bangladesh; a Staten Island couple whose home was damaged by Hurricane Sandy; and a fast-food worker from Brooklyn.

Mr. de Blasio’s successor as public advocate, Letitia James, who had been a city councilwoman, was also inaugurated on Wednesday, as was the new city comptroller, Scott M. Stringer, who had been the Manhattan borough president.

Children played an unexpectedly prominent role in the swearings-in of both Ms. James and Mr. Stringer.

Dasani Coates, the 12-year-old girl at the center of a recent New York Times series about the plight of the 22,000 homeless children in New York City, was called upon by Ms. James to hold the Bible while she was being sworn in.

In the series, Dasani and her family — her parents and seven siblings — were living in a decrepit room in a homeless shelter in Brooklyn.

On Wednesday, Dasani looked happy but slightly nervous, chewing gum as she solemnly watched Ms. James take the oath of office.

Afterward, Ms. James held Dasani’s hand during her speech, and referred to her as her “new BFF.”