In October 1918, San Francisco Health Officer William Hassler successfully lobbied the Board of Supervisors to make mask-wearing mandatory as a measure against the pandemic flu.

In November, Hassler was fined $5 for not wearing his mask, while he was attending a boxing match.

Hassler paid his fine on the spot, “admitting that his mask may have dropped a bit while he was smoking a cigar.”

Here’s the Nov. 20, 1918 San Francisco Chronicle article about the incident, which noted that a police photographer there caught many of the town’s most famous men breaking the mask law. “Many of them were without masks. That is how Chief White knew their identities.”

Also lobbying for the mask law was Mayor James Rolph, who attended the same boxing mask, leading to this Nov. 21, 1918 headline:

*Completely* by coincidence, effective Nov. 21, Rolph lifted San Francisco’s mandatory mask order. "Requests by the health department to conserve gauze amounted to little as residents joyously ripped the hated masks from their faces & unceremoniously tossed them in the streets."

On Jan. 10, 1919, following a resurgence of the influenza, San Francisco reimplemented mandatory masking, which lasted until Feb. 1.

All this information comes from the University of Michigan’s “Influenza Encyclopedia” (and articles cited therein), specifically its article on San Francisco: http://www.influenzaarchive.org/cities/city-sanfrancisco.html#