Barbara Lee, a progressive lawmaker known for her lone vote against military force after the Sept. 11 terrorist attacks, won the mayor’s race in Oakland, Calif., less than four months after she retired from a decades-long congressional career.

Oakland, a city of about 436,000 residents across the bay from San Francisco, has struggled to bounce back from the coronavirus pandemic shutdowns, and frustrated voters last year recalled Mayor Sheng Thao after she had served less than two years in office. Ms. Lee, 78, was seen in the city as a trusted and experienced voice who could stabilize Oakland and help guide it out of crisis.

Her rival, Loren Taylor, a former member of the City Council who ran as more of a moderate, conceded on Saturday after a dayslong vote-counting process. Mr. Taylor, 47, had gained traction with his detailed plan for improving Oakland, and appealed to voters who said they were increasingly fed up with crime and governance problems in the city.

In the latest vote tally, Mr. Taylor trailed Ms. Lee by more than 4,700 votes, a gap that is unlikely to be closed by the remaining ballots. Mr. Taylor has received 45 percent of the vote and Ms. Lee 50 percent.

After Mr. Taylor’s concession, Ms. Lee said she would address the most pressing problems in Oakland, working to unite a deeply divided city. “I accept your choice with a deep sense of responsibility, humility and love,” she said in a statement.

Mr. Taylor said he hoped that Ms. Lee would fulfill her commitment to bring Oakland together by listening to those who had voted for him.