I think there are two possible answers to this:
AuroraSan Francisco

Aurora because it was actually considered to be in California when Twain lived and worked (mined/milled) there in 1862. I learned this in RKR's MT A-Z compendium, and that it was found to be actually barely within Nevada's borders after a later (1874) survey.
So: is it to be considered that Twain lived in Aurora, CA before living in Frisco? Or is it to be considered that he only *thought* he was in California, whereas he was really yet in Nevada?
 - B. Clay Shannon