The Alexander Valley is located at the northern end of Sonoma County and has roughly 15,000 acres under vine. The "Alexander Valley" designation was historically used to label wines produced exclusively within the Russian River's floodplain, but it's now found on Alexander Valley wines that are produced farther afield. Thanks in part to the broader definition of its territory, the Alexander Valley is now home to numerous microclimates and a wide range of varieties, of which Cabernet Sauvignon remains the most widely planted.
During the growing season, cool morning fog rolls up the Russian River Valley and typically burns off by the hot, sunny afternoon. On the warm valley floor, Cabernet Sauvignon has yielded the best Alexander Valley wines. Other Alexander Valley red wines, such as Zinfandel and Merlot, are also planted widely, as are Chardonnay, Sauvignon Blanc, and even Gewurztraminer and Riesling. The latter two cool-climate varieties fare best on the hills near Mendocino.