Updated 11:13 p.m.

Lori Lightfoot, a former federal prosecutor who later led the city’s police board, scored a landslide victory Tuesday to become Chicago’s first black woman and openly gay mayor.

The 56-year-old Lightfoot is a first-time elected official and assumes control of a cash-strapped city from Mayor Rahm Emanuel – a centrist Democrat who was a White House chief of staff and congressman before serving eight years as mayor.

Lightfoot easily defeated Cook County Board President and county Democratic Party leader Toni Preckwinkle, a union-backed candidate once considered a favorite for mayor until becoming tainted by a City Hall corruption scandal.

With 97 percent of precincts counted, Lightfoot won 74 percent of the vote with Preckwinkle drawing only 26 percent, according to the Chicago Board of Election Commissioners.

“Thank you, Chicago. From the bottom of my heart, thank you,” a beaming Lightfoot told her supporters shortly after 9 p.m. in a speech punctuated by fist pumps and waves to the crowd.

“In this election, Toni and I were competitors, but our differences were nothing compared to what we can achieve together. Now that it’s over, I know we’ll work together for the city we both love,” she said. “Today, you did more than make history. You created a movement for change.”

Then, in framing the rags-to-riches political climb she made from longshot to victor, she invoked Martin Luther King, Jr.

“When we started this journey 11 months go, nobody gave us much of a chance. We were up against powerful interests, a powerful machine and a powerful mayor. But I remembered something Martin Luther King said when I was very young. Faith, he said, is taking the first step when you can’t see the staircase. While we couldn’t see the whole staircase when we started this journey, we had abiding faith,” she said.

Earlier, Preckwinkle appeared before her supporters at a Hyde Park restaurant and conceded defeat during a speech interrupted several times by chants of “Toni! Toni! Toni!”

“This may not be the outcome we wanted, but while I may be disappointed, I’m not disheartened,” said Preckwinkle, who will remain as county board president. “For one thing, this is clearly an historic night. Not long ago, two African-American women vying for this position would have been unthinkable. While it may be true we took different paths to get here, tonight is about the path forward.”

Both candidates branded themselves as progressive and independent in a city that’s been synonymous with Democratic machine politics and political bossism for most of the past century.

Emanuel had been fundraising to run for a third term this year, but his shocking announcement in September that he would not run for re-election set off a free-for-all unlike any other mayoral race in living memory.

Lightfoot and Preckwinkle narrowly emerged from an unprecedented field of 14 candidates in the first-round election on Feb. 26. Under the rules of Chicago’s nonpartisan mayoral elections, Tuesday’s runoff was necessary because nobody won a majority of the votes in the first round.

That’s when Lightfoot finished a surprising first with 17.5 percent of the vote, despite being a political neophyte and attracting less campaign cash or endorsements than many of her rivals. Preckwinkle squeezed into the second runoff spot ahead of William Daley, the son and brother of Chicago’s two longest-serving mayors, who had been by far the best-funded candidate.