Which is one reason why "Silicon Valley" never included San Francisco: There's no place to build fabs there. It's only been in the last 20 years with the rise o

Which is one reason why "Silicon Valley" never included San Francisco: There's no place to build fabs there. It's only been in the last 20 years with the rise of software-only startups that everybody decided they needed to be in the city proper (mostly because VCs wanted to live there and they wanted their funded companies to be close by). Not that San Mateo and Santa Clara are much easier to find real estate in these days, but they're easier than San Francisco. Just not as cool.