There is more to the story. Stevenson had tuberculosis (then called “consumption.”) Before there were treatments, the main thing you did was look for a dry, arid climate which apparently made the symptoms of the disease less severe (like Arizona—gunslinger Doc Holliday is an example of someone who went to a desert climate to find relief). Much of Stevenson’s life journey was trying to find a climate that would not exacerbate or would ideally “heal” his tuberculosis.
San Francisco was definitely not the place to be because of all the fog, and it had a dramatic effect on him. I think before that, he had arrived in Sacramento (same problem, with the fog from the delta). So he tried to get away from the City and the fog.
He went to Napa Valley (Calistoga was known as a health sanatorium, with hot springs and mud baths that supposedly had restorative powers), but if you’ve spent time in Napa Valley you know that during much of the year and especially in the summer, the fog from the coast basically comes in every night (and usually lifts the next morning around 10 or so).
So the only solution was to try to get above the fog layer. He did that by going up Mr. St. Helena to the old abandoned mining camp.
The other thing I thought was interesting in his account, “The Silverado Squatters,” was his description of constantly hearing buzzing noises—he couldn’t figure out what the sound was although it was all all around him. Somebody finally told him that there were rattlesnakes in the mining camp—in fact, the camp was infested with them. Stevenson and his family (and their dog) were fortunate not to get bitten.
He eventually went to Hawaii and the South Pacific.
I read a short story by Stevenson last year. I realized why his books fascinated me when I was a kid—the man knew how to tell a tale.