There isn't one reason. I think a lot of people really underestimate the power of the Silicon Valley brand. Silicon Valley has over 60 years of history as bein

There isn't one reason. I think a lot of people really underestimate the power of the Silicon Valley brand. Silicon Valley has over 60 years of history as being a place where tech companies come from. It has had nearly the same amount of history of venture capital investment. Just like the United States was branded as the place where roads were paved of gold, Silicon Valley is branded as the place where dreams become reality. This is powerful. It means we draw in the young, the dreamers, the motivated, the intelligent, the networkers and (generally) the doers. We drain other areas of their talent. We drain entire countries of talent. Plus we have three world class universities with stringent entrance requirements that put out huge numbers of people that were literally surrounded by peers starting companies in fields that have easy financing (berkeley - tech/cleantech/biotech, ucsf - biotech, stanford - tech/cleantech). A few National Labs (Berkeley, Livermore and SLAC) and the NASA Ames research center didn't hurt either. On top of that, we have an area where nearly everyone is a potential beta tester. We're talking about a population of 7 million people who all know someone in tech or related to tech that are willing to try out your random product. Who will talk about it in the coffee shop. There is a large enough initial user base in the bay area alone to get you over the network effects threshold which is important to a whole host of companies (not all of course). The reason you don't see this in other places is because it took decades and decades to happen and several cultural anomalies were instrumental in it continuing. A big one was that startup founders who got lucky in the early days also didn't hoard their money. They reinvested it in the next generation of companies which really helped keep SV strong. They also tended not to move. Once you come here, you stay (your kids on the other hand are a different matter).