Breed ordered businesses closed and issued a citywide shelter-in-place policy effective on March 17, at a point when San Francisco had fewer than 50 confirmed coronavirus cases. (California Governor Gavin Newsom followed with a similar statewide order a few days later.) On that date, New York City already had more than 2,000 positive cases. But New York Governor Andrew Cuomo and New York City Mayor Bill de Blasio, reluctant either to shutter schools or issue a stay-at-home directive for the nation’s largest city, didn’t take similar action for several days. By the time New York City fully shut down on March 22, more than 10,000 cases were reported across its five boroughs.

Breed’s aggressiveness was not initially popular. As she ratcheted up the city’s social-distancing mandates, prominent San Franciscans began calling one of the mayor’s political mentors, Senator Kamala Harris. “London Breed’s about to shut down the city,” they complained, Harris told me. She told them to trust Breed.

“She took incredible political heat and criticism,” Harris said, “and she had the courage to make a decision that she in her gut, based on science and the research she did, told her this was the right thing to do for her people, even when other people couldn’t see it yet.”