For history, especially romantic history, no other AVA in California compares with Sonoma Valley. In addition to being the site of the ragtag 1846 Bear Flag revolt, which eventually secured Alta California for the US rather than Mexico, it had the last of the Franciscan missionary vineyards, one of the earliest commercial vineyards north of San Francisco (General Mariano Vallejo appropriated the Franciscan plantings), and, courtesy of public relations master Agoston haraszthy, the first great winery name of northern California, Buena Vista (now owned by boisset). In more modern times, its Hanzell Vineyard started the rush to using French oak barrels to age California wines and thereby revolutionized their style, most especially Chardonnay’s. The valley runs parallel to the Napa Valley to the east, its southern extremity doubling as the Sonoma portion of carneros. A long, thin comma of a trough in the coast ranges, it warms markedly from south to north because San Francisco Bay’s influence dwindles mile by mile. Steep mountains on each side make it geologically as well as climatically complex. Some of its memorable wines portray that diversity: Zinfandel, Gewurztraminer, Pinot Noir, Chardonnay, and Cabernet Sauvignon. Sonoma Mountain (see above) is a sub-AVA. The Monte Rosso Vineyard, planted in 1838 by Louis M. Martini, looms large over the valley, with views of San Francisco on clear days, and produces Cabernet Sauvignon and Zinfandel fruit for several producers, including gallo’s Louis M. Martini Winery in Napa.