Sonoma Valley AVA is an appellation in California, USA. It is the oldest wine region north of San Francisco and is located on the western side of the Mayacamas Mountains, which separate it from the Napa Valley. The valley nearly touches the Russian river valley to the north-west and reaches the Sonoma portion of Carneros in the south. With steep mountains on either side there are great variations in climate and geology, which gives way to many different grape varieties and styles. The most notable varieties are Chardonnay and Zinfandel but also Cabernet and Merlot from hillside sites.