What was the last year the penny was minted in San F?

Circulation cents were minted regularly up to 1955. Coinage was suspended, then resumed from 1968 until 1974.

The mint decided to end circulation coin production at San Francisco because all proof coins were now being minted there and the facilities were needed for those coins. Also, with only limited runs of circulation coins compared to Philadelphia and Denver, they did not want to create "instant rarities".

So to be technical, minting of proof coins at San Francisco means that S-mint cents are still being made regularly, just not for circulation.