Final answer:
Tulare County is the largest producer of milk in California, situated in the highly productive Central Valley which is essential for meeting the milk demand in populous regions.
Step-by-step explanation:
The county in California that produces the most milk is Tulare County. California's Central Valley, home to Tulare County, is a highly productive agricultural area.
Despite California being known for other agricultural products like tomatoes, grapes, almonds, and wine, it is also the largest producer of milk in the United States. Tulare County outpaces other counties in milk production thanks to its vast dairy operations that meet the high demand for milk in heavily populated areas.