You mean San Mateo County? Santa Clara County is roughly 1/3 white, 1/3 Asian, 1/3 Hispanic, with 2% or less black.
yes, San Mateo County indeed
(thought, you can visit the Bay Area and see a great deal of diversity in most of it, especially if your vista includes at least a 5 or 10 mile frame of reference....allowing for a couple of “mostly-ghetto” localities like most of Oakland and Richmond for black people and Marin for white people, and so forth, but just go ten miles and you get super-diversity entoto).
yet, there is change afoot, with tons of Asians moving in and some black and even now a little visible Latino exodus)