Tonight, history was made in Chicago. Two African American women won the top two slots.

Chicago’s next mayor will be an African  American woman.

Farewell to Rahm Emanuel; your disgraceful historic legacy will be closing 50 public schools in a single day.

William Daley, the business establishment’s candidate, came in third. Au revoir.

Paul Vallas, school privatizer supreme, trailed the field.

CHICAGO — Two African-American women are headed for a runoff in the Chicago mayor’s race, setting up an election that will make history.

Lori Lightfoot, a former federal prosecutor and sharp critic of the status quo at City Hall, and Toni Preckwinkle, the county board president and chairwoman of the county’s Democratic Party, will face one another in a runoff election set for April, according to The Associated Press.

The third top vote-getter — William M. Daley, a member of Chicago’s political dynasty of Daleys — earlier conceded defeat.

Either Ms. Lightfoot or Ms. Preckwinkle would be the first African-American woman to lead the nation’s third largest city, succeeding Mayor Rahm Emanuel as mayor. Only one other woman, Jane Byrne, has been elected mayor, in 1979. If Ms. Lightfoot were to win, she also would be the first openly gay mayor of Chicago.

Ms. Preckwinkle, 71, a long established politician who has often been urged to run for mayor, had been widely expected to do well in Tuesday’s balloting amid a cast of 14 candidates. The success of Ms. Lightfoot, 56, who has never run for elective office before, was far more surprising; she was less well known in Chicago’s political sphere and had far less money.

Her win, too, was seen as something of a rebuke to Mr. Emanuel’s tenure as mayor and to Chicago’s old political history. Ms. Lightfoot had tried to define her campaign as a rejection of machine politics and a refocusing on Chicago’s struggling neighborhoods, not just its gleaming downtown.

Ms. Lightfoot emerged at a gathering of supporters late Tuesday night, and seemed to take note of people who hadn’t expected her success. To applause, she called out: “So what do you think of us now?” She added: “This, my friends, is what change looks like.”

The historic nature of the runoff was not lost on Ms. Preckwinkle’s supporters, who gathered at a party on another side of town. The crowd cheered when Bridget Gainer, a county commissioner, noted from the stage that Chicago city would, one way or another, have an African-American woman as mayor later this year.