California

Nearly three-quarters the size of France, California accounts for nearly 90 percent of American wine production.  If California were a separate country, it would be the world's fourth-largest wine producer. 

The wine regions of California are often divided into 4 main regions:
North Coast - Includes most of North Coast, California, north of San Francisco Bay. The large North Coast AVA covers most of the region. Notable wine regions include Napa Valley and Sonoma Co., Mendocino and Lake Co.
Central Coast - Includes most of the Central Coast of California and the area south and west of San Francisco Bay down to Santa Barbara Co.  Notable AVA include Central Coast AVA , Paso Robles AVA..
South Coast - Includes portions of Southern California. A notable wine region in this area isTemecula Valley AVA.
Central Valley - Includes California's Central Valley and the Sierra Foothills AVA including Lodi AVA.