Established in 1981, the Napa Valley AVA covers 225,300 acres of land, encompassing almost the entire county of Napa and is home to 400 wineries. Within that area, there are 45,000 acres of vineyards planted. Cabernet Sauvignon is king in Napa Valley with a total of 18,200 acres, and Chardonnay is the most widely planted white wine variety with 7,300 acres. Napa produces about five percent of total California wine.
The Napa Valley is bordered by two mountain ranges—the Vaca on the east and the Mayacamas, rising well above 2,000 feet and bordering the adjacent Sonoma County, on the west. Mt. St. Helena (4,343′) stands sentry at the northern end of the appellation where the valley ends at the town of Calistoga. This is the warmest locale in the region. About 30 miles away, near the city of Napa, the southern end of the valley opens to San Pablo Bay, an interconnecting arm of the San Francisco Bay system.
A uniquely diverse winegrowing appellation, the Napa Valley formed—much like the rest of the North Coast—through a geological evolution active with colliding tectonic plates (large pieces of the earth’s crust), volcanic activity and changes in sea level as water alternately advanced and retreated over the southern end of the valley several times. As a result of these geological events that took place over a 60-million-year history, the Napa Valley has soils of volcanic, maritime and alluvial origin, with more than 30 different types identified.
Defined by mountain ranges and a proximity to the Pacific Ocean, the Napa Valley enjoys a temperate climate with a long growing season of sunny, warm days followed by cool evenings. Within the Napa Valley AVA, there are 14 other AVAs with distinct microclimates and terrains formed by a varied topographical configuration of hills, exposures and elevations. The Napa Valley AVA is also part of the North Coast AVA.