Part of San Francisco.
They are part of San Francisco because the state of California explicitly wrote them into the legal boundary description of the City and County of San Francisco in state law. [reddit](https://www.reddit.com/r/sanfrancisco/comments/3nltn7/til_the_farallon_islands_are_a_part_of_the_city/)
Historically, San Francisco’s claim is tied to the Gold Rush era, when the Farallones were heavily used by San Franciscans as a food source, especially for seabird eggs that were collected and sold in the city. When state legislators later formalized county boundaries, they included a clause stating that “the islands known as the Farralones (Farallons) are a part of said city and county,” which is why they remain legally within San Francisco’s jurisdiction today despite being about 30 miles offshore. [en.wikipedia](https://en.wikipedia.org/wiki/Farallon_Islands)
There was no single dramatic event like a treaty or riot that “transferred” the Farallon Islands to San Francisco; instead, they were written into San Francisco’s boundaries in 19th‑century California law largely because of their practical use to the city during the Gold Rush era, especially for egg harvesting and navigation. [kalw](https://www.kalw.org/education/2020-03-19/how-did-the-farallon-islands-get-to-be-part-of-san-francisco)
In the mid‑1800s, San Francisco exploded in population during the Gold Rush, creating a severe food shortage, and entrepreneurs began collecting vast numbers of seabird eggs from the Farallones to sell in the city, leading to intense competition and violence known as the “Egg War.” Because San Franciscans were regularly exploiting and visiting the islands and because they sat at the maritime approach to the bay, state legislators later codified county boundaries so that the “islands known as the Farallones” were declared part of the City and County of San Francisco, reflecting an existing economic and geographic relationship rather than responding to one specific triggering event. [en.wikipedia](https://en.wikipedia.org/wiki/Farallon_Islands)
No