I'm not sure what's the point you're making with the gold rush migration, but most of the population to California came after Model T, and it was during and after the World Wars that California saw much of its population growth. Michigan had more population than California up until 1930s.

https://en.wikipedia.org/wiki/List_of_U.S._states_by_histori...

I believe the population growth has contributed to the growth of Silicon valley significantly. There seems some feedback loop between the population growth and the industry growth.