The Board of Supervisors of the City and County of San Francisco codified the design of the current flag on December 16, 1940.

Gamble's concept depicted a black phoenix rising from gold flames on a white field.

When the long-lived phoenix feels death is near, it builds a nest of aromatic wood and sets it afire.

The motto refers to the city's then-recent experience during the Spanish–American War as the embarkation point for troops to the Philippines in 1898.

In the early 1930s, the San Francisco Mayor's office began using a version of the police and fire department flags that featured only the symbolic elements.

The yellow border, now reproduced as a part of the flag, was originally intended to be a gold fringe, but mistakenly became incorporated into the design.