There is this great article on the history of the dairy industry here. Marin county "led the way in production of fine dairy products."
We have grass fed cows, producing amazing dairy here. Things didn't change much here. Because of the Marin Agricultural Land Trust, this county escaped the development that was going to be inevitable leaving us with a pristine pastoral landscape that has not changed in the time the rest of the US has drastically grown.
Every time I tell people in San Francisco I live in Marin county they say things like, "You are one of the luckiest people in the world..." It is true, I am.