Not really SV is built on defense funding from the 40's onwards - widespread h1b is much later

Why stop there? What about Dave and Bill's shed in '38? Or maybe it was Leland opening the university in 1891? Surely that was the start of Silicon Valley?

Actually, it was probably Rock and the Traitorous Eight in '57 as the genesis of Silicon Valley. And you might be familiar with some of these US immigrants, none of whom were H1b's: Jerry (yahoo), Sergei (google), Pierre (ebay), Elon (paypal).