Mendocino lies just to the North of Napa and Sonoma. It's wine history dates back to the 1860's, when immigrants to the area planted the first vines. Most of the wine produced in Mendocino was consumed only by the locals, and the isolated nature of the area due to mountains prevented a great deal of export. Even to this day, the area is somewhat unknown and isolated as far as wine production is concerned. Mendocino is very large and has two different major climactic regions, that are on either side of the coastal mountain range. Except for the cooler Anderon Valley, the wine producing areas are too far ashore to benefit from any cooling influences of the pacific, so most of Mendocino is in a continental climate zone. Mendocino contains 8 AVA's, which I will now list in detail.
Anderson Valley is formed by the Navarro river, that empties into the pacific to the North. Because of the river's northerly path, Anderson Valley is cooler towards the north. Lots of sparkling wines made from Chardonnay and Pinot Noir are produced from the cooler northerly section of the valley. In the south, where it is a little warmer, Sauvignon Blanc and Merlot are more common.
Mendocino ridge is actually an area within Anderson Valley, and it is the only AVA in the United States that does not cover one contiguous area. This is because it applies only to the elevations that are above the fog line (1200 feet) on the easter slopes of the Anderson Valley. The most common grapes grown here are Syrah, Zinfandel, Merlot, and Cabernet Sauvignon.
Cole Ranch is the smallest AVA in the United States, covering only 61 acres. It is home to only one grower that goes by the same name, and is located at 1,400 to 1,600 feet. The main grape grown on the ranch is Cabernet Sauvignon, but they also grow a small amount of Chardonnay and Riesling.
Potter Valley is most famous for its dessert wines, made from grapes affected by botrytis. As in most areas that produced botrytized wines, the moisture in this area can cause a great deal of problems for the grape growers, including the likelihood of frost. The most grapes grown here are Riesling and Semillon, and some small amounts of Chardonnay, Pinot Noir, and Sangiovese.
Redwood Valley receives a small amount of cooler air from the russian river, helping preserve the acidity in the most common varietal grown here, Syrah. There are also small amounts of Zinfandel, Cabernet Sauvignon, and Petite Syrah.
McDowell Valley is just south Of Ukiah, the main city in Mendocino. It features volcanic soil and most of the vineyards are planted between 850-1,000 feet. Rhone varietals like Syrah, Mouvedre, and Grenache are the most common grapes planted here.
Yorville is a relatively new wine area, and to date only has a few wineries. It is most well known for growing Sauvignon Blanc and other Bourdeaux style grapes.