This ranking only counts San Francisco city/county. I think the OP was referring to the San Francisco Bay Area [1]. It is comprised of nine Bay Area counties a

This ranking only counts San Francisco city/county. I think the OP was referring to the San Francisco Bay Area [1]. It is comprised of nine Bay Area counties and has quite a bit of open space, as well as federal, state, county, and city parks. [1] https://en.wikipedia.org/wiki/San_Francisco_Bay_Area https://en.wikipedia.org/wiki/San_Francisco_Bay_Area