[beambot]

They were most certainly caused by local efforts in the 1950s. The reason the Silicon revolution happened in Silicon Valley had everything to do with Cold War radar systems. I suggest watching Steve Blank's Secret History of Silicon Valley to get a better historical perspective:

https://steveblank.com/secret-history/

[hogFeast]

The "silicon revolution" happened at Bell Labs, rising out of their need to replace vacuum tubes. Shockley only moved to SV because his mother lived there, and she was sick. And it just so happened that Terman invested heavily in making Stanford into a college with heavy links to industry. It is true that military research was a factor in this process (again, semi-coincidentally...Bell Labs invested heavily in military research because they believed, correctly at first, that this would protect them from being broken up...radar was invented, in its modern form, in the UK and developed heavily by Bell Labs/MIT) but there were other factors. SV's pre-eminence looked at from the 1950s was extremely non-obvious however (Boston was the centre of the VC world, MIT and Bell Labs led in research).

[clairity]

the cold war and american science by stuart leslie is a good accounting of the overall history from the early 20th century to the 80s: https://www.goodreads.com/book/show/212074.The_Cold_War_and_...