In 1981, Napa Valley became California’s first federally-recognized American Viticultural Area (AVA). About an hour by car from San Francisco, it is compact (5 miles across at its widest point), representing only about 4% of wine production in the Sunshine State, which has not dampened its prowess as a wine region. Impressive facts include its fairly pure Mediterranean climate and its almost-incredible diversity of soil types(12 distinct soil orders), combined with varied topography, including protective mountains, which can produce different microclimates.Napa Valley has 16 other AVAs nested within it, each with distinct characteristics. If you see “Napa Valley” on a wine label, it means 85% of the grapes used to make the wine came from within the valley, but not necessarily from one of the sub-regions. Cabernet Sauvignon, Chardonnay, Pinot Noir, and Merlot are the four most-planed grape varieties in Napa Valley. A Prussian immigrant, Charles Krug, established Napa’s first winery in 1861 on an impressive 540 acres of land his wife—Carolina Bale—inherited. Krug had studied winemaking with Hungarian immigrant Agoston Haraszthy, among others, starting in the 1850s. Haraszthey, among other accomplishments, introduced more than three hundred European grape varieties to California. Indeed, in the 19thcentury, vine planting were often a patchwork of different varietals and wines were often “field blends.” Nonetheless, Krug was, if not prescient, then lucky and knowledgeable, having started the growthtoward what is today America’s wine capital. Today, great precision is applied to Napa wine creation. “We have an intimate understanding of the connection between terroir and vine,” says the Napa Valley Vintners association,“and have realized just how the diversity of Napa Valley’s soil, climate and terrain allow us to grow distinctive wines from specific areas within the valley.” The other AVAs in the valley include: Atlas Peak, Calistoga, Chiles Valley, Coombsville, Diamond Mountain District, Howell Mountain, Los Carneros, Mt. Veeder, Oak Knoll District of Napa Valley, Oakville, Rutherford, St. Helena, Spring Mountain District, Stags Leap District, Yountville and Wild Horse Valley. The valley is createdby the VacaMountains to the east and the Mayacamas to the west and north, with Sonoma County on the other side.Internal hills create smaller valleys. The Rutherford Bench lies in the center of the valley floor. Southern-end soils aremainly made up of ancient oceanic sediments whileat the northern end of the valley the soil featuresa large volume of volcanic lava and ash. Small hills that emerge from the middle of the valley floor near Yountville revealthe Napa Valley’s ancientvolcanoes.The valley is about 30 miles long. The valley’s southern end opens to San Pablo Bay, and is cooler; the northern end is more sheltered,andwarmer.The mountains and hills block rainy weatheron the eastern side, a phenomenon known as a “rain shadow” where onone side of the mountains, wet weather systems drop rain,while on the other sidesuchprecipitation is blocked; thusthis area is much drier than the rest of the valley.