Chicago will swear in its first black female and first openly gay mayor Monday, concluding Lori Lightfoot's astonishing, yearlong rise from near anonymity to leader of the nation's third-largest city.

Lightfoot defeated Cook County Board President Toni Preckwinkle in a landslide runoff election April 2, claiming 73% of the vote and winning all 50 wards. She also won a majority of the white vote, the black vote and the Latino vote.

"We are going to transform our city," Lightfoot said last week. "No one person, no one leader—even if it's a woman—can change the city alone. We must do it together.”

The former federal prosecutor and political outsider drew little notice last May when she announced her long-shot challenge to Mayor Rahm Emanuel for the Democratic mayoral nomination.

When Emanuel declined to seek a third term, several Democrats with far more name recognition than Lightfoot leaped into the political fray. But it was Lightfoot who claimed the most votes in the field of 14 in the February election, although she failed to gain the 50% threshold required to avoid a runoff.

The runoff campaign grew bitter. Preckwinkle supporters tried to link Lightfoot, a former federal prosecutor and city Police Board president, to police-involved shootings and a criminal justice system viewed as biased against African Americans.

U.S. Rep. Bobby Rush, who is black, had warned that the “blood of the next young black man” killed by police would be on the hands of Lightfoot supporters if she won.

“We can and we will build trust between our people and our brave police officers so that the communities and police trust each other–not fear each other,” Lightfoot assured supporters in her victory speech.

Lightfoot also inherits a public school system struggling with dwindling enrollment and poor academic results. Chicago Teachers Union President Jesse Sharkey warned Friday that schools have reached a "breaking point," citing a shortage of nurses, counselors and social workers among other issues.

Lightfoot has promised a "reallocation" of resources and expansion of partnerships with community groups to increase the number of educational support positions.

Lightfoot is married to Amy Eshleman, a former assistant commissioner of the city's public library system. They live on the near northwest side of the city with their daughter.

Lightfoot was the first of three openly LGBTQ candidates across the nation to win mayoral races within a few weeks. Tampa’s former police chief Jane Castor made history last month, becoming the first LGBTQ major elected in a southeastern U.S. city, and Satya Rhodes-Conway also was elected last month as Madison, Wisconsin.

Before their victories, only two out lesbian candidates, Seattle's Jenny Durkan and Houston’s Annise Parker, have served as mayor of one of America’s 100 most populous cities.

"A lot of little girls and boys are watching," Lightfoot said in her victory speech. "They are watching us and they are seeing the beginning of something, well, a little bit different. They are seeing a city reborn. A city where it doesn't matter what color you are . . . where it doesn't matter who you love, just as long as you love."

Contributing: Aamer Madhani