Chicago is expected to elect its first black woman as mayor with two African-American women headed for a runoff election this year.

Lori Lightfoot, a former federal prosecutor, and Toni Preckwinkle, the county board president, are leading the top two spots on Chicago’s mayoral election night based on unofficial results posted on the city’s Board of Election, with 92.61 per cent of the precincts reporting.

There were a total of fourteen candidates on the ballot seeking mayorship, the highest number in Chicago history.

The concession of William “Bill” Daley, the third place candidate, on Tuesday night confirms that the next mayor – whether it is Ms Lightfoot or Ms Preckwinkle – will be a black woman. Ms Lightfoot could also be Chicago’s first openly gay mayor.

Mr Daley is a member of the famous political family known for its deep roots in Chicago, with his father and brother – Richard J Daley and Richard M Daley, respectively – serving as the windy city’s mayor for more than 40 years combined.

For first time in decades, Chicago faces life without a Daley in charge Show all 8 1 /8 For first time in decades, Chicago faces life without a Daley in charge For first time in decades, Chicago faces life without a Daley in charge 1989: Richard Daley after his first election win AP For first time in decades, Chicago faces life without a Daley in charge 1955: Richard J Daley is elected as Mayor of Chicago. He becomes known as the last of the big city bosses and runs a well-organised Democratic party political machine AP For first time in decades, Chicago faces life without a Daley in charge 1968: A storm of protest followed allegations that Daley told police to 'shoot to kill' rioters in disturbances following the death of Martin Luther King AP For first time in decades, Chicago faces life without a Daley in charge 1976: President-elect Jimmy Carter and Vice-President Nelson A Rockefeller at Daley's funeral at Nativity of Our Lord Catholic Church after he died of a heart attack after nearly 22 years as mayor AP For first time in decades, Chicago faces life without a Daley in charge 2000: High-rise housing schemes (built by his father) are knocked down. The schemes had given the city the reputation as one of the most segregated in the US AP For first time in decades, Chicago faces life without a Daley in charge 2003: Bulldozers are sent in under the cover of darkness to tear up an airstrip and turn it into a park in highly contested scheme AP For first time in decades, Chicago faces life without a Daley in charge 2009: Chicago loses its bid for the 2016 Olympics despite a multi-million dollar effort and an endorsement from President Obama AP For first time in decades, Chicago faces life without a Daley in charge 2010: Daley announces he is quitting as Mayor AP

Before running for mayor, Mr Daley served as Barack Obama’s White House chief of staff. He conceded after receiving 14.7 per cent of the vote. Ms Lightfoot had 17.5 per cent and Ms Preckwinkle had 16 per cent.

"One of them will have the honour of being the next mayor of Chicago," Mr Daley said.

In her election night speech, Ms Lightfoot thanked her supporters and encouraged them to join her in the fight against Chicago’s political machine.

“This campaign was powered by you," Ms Lightfoot said, before adding "this is going to be a race that comes down to the inches" and expressing gratitude to her supporters for their courage "to stand with our campaign against the machine".

Ms Preckwinkle told her supporters: “Our fight is far from over, and there's a lot more work to do.

"We may not yet be at the finish line, but we should acknowledge that history is being made.

"It's clear we’re at a defining moment in our city’s history. But the challenges that our city faces are not simply ideological."

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According to the Chicago Board of Elections, a candidate will need to earn more than 50 per cent of the votes to avoid a run-off election. If no candidate has reached that threshold, the top two candidates will face each other in a run-off election scheduled for 2 April.

Incumbent Mayor Rahm Emanuel did not run for re-election. He has served as mayor for two terms since 2011.