St Helena is one of the Napa Valley's key subregions, located in the shadow of the 4345ft (1325m) Mount Saint Helena, from which the small town takes its name. The AVA, given in 1995, specializes in rich red wines made from Cabernet Sauvignon and, to a lesser extent, Merlot. These are made by some of California's most notable names, including Beringer, Joseph Phelps, Turley and Duckhorn Vineyards.

?Napa Valley Vintners
The town and its vineyards are located where the valley narrows substantially, about 15 miles (25km) north of Napa. At this point, the mountains of the Vaca and Mayacamas ranges close in on one another, pitting Spring Mountain and Diamond Mountain in the west against Howell Mountain in the east. St Helena's prestigious neighbors, Rutherford and Oakville, lie just to the south.
The AVA covers 9000 acres (3645ha) of densely packed vineyards in this bottleneck, and is home to more than 30 wineries. Among these is Beringer, one of California's oldest continuously operating wineries, founded by Jacob Beringer and his brother Frederick in 1875. In recognition of the contribution the Beringer family estate has made to Napa Valley and its wine industry, the site was added to the National Register of Historic Places in 2001. Next to Beringer Vineyards is the Charles Krug winery, established by the eponymous German-American who is often credited as being the "father of Napa wine".
St Helena showcases the climatic differences between the northern and southern ends of the Napa Valley. The southern part of the valley abuts San Pablo Bay, meaning that more southern AVAs like Carneros and Oak Knoll District are cooled by the famous San Francisco Bay fog, as well as ocean breezes from the bay. The ocean's influence gradually fades with each increase in altitude and distance from the ocean, so St Helena receives very little benefit from this climatic phenomenon.
Consequently, St Helena is one of Napa's warmer appellations, surpassed only by Calistoga, which lies even further up the valley. This makes it well suited to producing rich, structured red wines from the key Bordeaux varieties, as well as Californian favorite Zinfandel. White wines are not common in St Helena, although a few more adventurous producers are making Sauvignon Blanc from St Helena vineyards.