North Coast's Napa Valley is California's most famous viticultural area (AVA), claiming some of the most expensive agricultural land in the world and producing wines of cult status. Its 16,000 ha of vines lie over a strip (40 miles long-5 miles wide) of diverse soils (clay, gravely, volcanic), with its northernmost end on the side of Mountain Helena and its foot in San Francisco Bay. The valley is framed by two mountains ranges Vaca (to the north) and Mayacamas (to the south), yet the main climatic influence is the cool wind and fog that is sucked in from San Pablo Bay during the afternoon, allowing grapes to ripen slowly and evenly. The area enjoys a variety of unique microclimates, as temperatures can vary dramatically as much as 15 degrees, from the north to the south end of the valley. These differences have led to the creation of several sub-AVAs (14 in total) including: Atlas Peak, Chiles Valley District, Diamond Mountain District, Howell Mountain, Los Carneros, Mt. Veeder, Oakville, Rutherford, St. Helena, Spring Mountain District, Stags Leap District, Yountville, Wild Horse Valley and Oak Knoll District. The Calistoga AVA is still pending approval. Both the Napa Valley designation and the sub-AVA name must appear on the wine label simultaneously, with the exception of wines from the Carneros AVA, which is shared between the Napa Valley and the Sonoma County. Cabernet Sauvignon is the undisputed king of Napa grapes, occupying over 45% of the vineyard acreage, followed by (predominantly) Chardonnay, Sauvignon Blanc, Chenin Blanc, Riesling, Zinfandel, Merlot, Cab. Franc and to a lesser extent Petite Sirah, Sangiovese, Barbera, Dolcetto.
