Moreover , during this time , food processing was the largest United States industry in both labor size and product value .
The California Santa Clara Valley , south of San Francisco , was the largest fruit growing and processing center in the world during the 1920s .
During this time , food processing was the largest United States industry in both labor size and product value .
The California Santa Clara Valley , south of San Francisco , was the largest fruit growing and processing center in the world during the 1920s .