North Coast's Sonoma County is California's largest AVA with 19,800 ha (2005) of vines. It has forever been the home of the meek and mild small grower as compared to the grandeur and might of neighbour Napa; more picturesque too, as much of the sandy, gravely loam land belonged to true orchards and fruit farms until the 1970s.
Sonoma Valley covers a small part of Sonoma County but its wines often outshine its illustrious neighbours in Napa County. Zinfandel, Pinot Noir, Chardonnay, and Cabernet Sauvignon are cultivated here with much success. Sonoma Valley has long enjoyed a special place in the history of California wine. The first vineyards in the valley were planted by Franciscan monks in 1823. In 1857 Agoston Haraszthy, one of the founding fathers of California's commercial winemaking, opened here the highly successful Buena Vista Winery.
Closer to the coast are the region's top producing AVAs for Pinot Noir and Chardonnay: Russian River, Sonoma Coast and Green Valley, while the slightly warmer Dry Creek and Alexander Valleys have earned a reputation as a hotspot for Cabernet, and increasingly, Zinfandel and Merlot.
Ridge, Teira, Williams & Selyem, Rochioli are definitely worth investigating.