California accounts for roughly 90 percent of the total aggregate production of wine in the US. According to the Wine Institute, California shipped 494 million gallons of wine in the US and abroad in 2003. The reputation of California wine is underscored by the fact that 70 percent of wine consumption is California made at the national level, with exports increasing by 30 percent.

Forty-six out of the 58 counties in California grow grapes covering 529,000 acres. A favorable Mediterranean type of climate and soil conditions makes wine production the largest agricultural activity in the state. Wineries consist of vineyards, processing (fermentation), storage and bottling. There are approximately1400 wineries in California, with Napa Valley having the highest concentration of over 400 wineries.

Most of the wineries in Napa Valley are small and family owned and has been in existence for over 80 years. Some of them are international such as Chateau Montelena, Freemark Abbey Winery and Heitz Wine Cellars. Napa Valley produces world-class red and white wines such as Chardonnays, Rieslings and Sauvignons.

Other than contributing to the $45 billion wine industry of California, many of the wineries contribute to the tourism industry as well. They offer wine tasting and wine tours that attract millions of tourists yearly. Some of the wineries don't allow visitors or some may require bookings months in advance. Some of the wineries offer gourmet picnic lunches with delicious menus and vintage wines in scenic locations. There are wineries in all the major cities and towns of Napa Valley.