In 1918, there was an anti-mask league in San Francisco.

In 1918, there was an anti-mask league in San Francisco, which objected to wearing masks to prevent the spread of influenza. They held meetings of thousands of maskless people. San Francisco was ultimately was one of the cities that suffered most from the Spanish Influenza pandemic 

Read more in the link below

https://www.influenzaarchive.org/cities/city-sanfrancisco.html