Bill de Blasio has been formally sworn in as New York's 109th mayor, the first Democrat to occupy the office in two decades.
De Blasio officially become mayor with a brief swearing-in outside his home shortly after midnight on New Year's Day. But later in the day, former U.S. President Bill Clinton administered the oath of office for the 52-year-old de Blasio in a formal ceremony at City Hall.
De Blasio took office with a vow to pursue a sweeping liberal agenda for the more than eight million residents in America's largest city.
"We are called to put an end to economic and social inequalities that threaten to unravel the city we love. And so today, we commit to a new progressive direction in New York."
De Blasio assumes control from three-term mayor Michael Bloomberg, a political independent who is credited with bringing down crime rates and making the city more environmentally friendly.
Bloomberg has been criticized by de Blasio and others for leaving the city sharply divided between high earners living comfortably and low-income residents who struggle to meet their expenses.
That income gap is one of de Blasio's biggest challenges. He called for a tax increase on the city's wealthiest residents to pay for his signature proposal, universal access to pre-kindergarten.