Here are some other interesting facts about the AVA:
The first Californian wine made from Bordeaux varieties (Cabernet Sauvignon and Malbec) was produced by the New Almaden Winery. There are many inaccurate statements commonly repeated about the winery; even the commemorative plaque that marks its location has at least two significant errors1. In 1852 Etienne Thee planted Vitis vinifera grapevines at the site. As was common at the time the variety was what is commonly known as "Mission", now identified as a little-known Spanish variety called Listan Prieto. Fellow Frenchman Charles LeFranc joined the company a few years later; unsatisfied with the quality of the wines produced he sent to France for cuttings from Bordeaux which were grafted onto the existing vines.
Within a short time Santa Clara County had more acres of vineyard than any other county in the state, with over 100 different varieties of grape being grown. At its peak there were over 120 wineries based here.
The Almaden winery is now a housing estate, and the brand that bears its name is based in Merced. However two other Santa Clara Valley wineries can trace their history to before Prohibition. Solis Winery was originally Bertero, and was founded in 1919. Kirigin Cellars is even older; it was previously called Bonesio Winery, founded in 1916.
The largest vineyard in the AVA is Dunne Ranch. This 1000 acre property has over 370 acres of grapevines - more than all of Santa Cruz County combined. Among them are around 300 acres of Chardonnay; this planting alone makes it the most prolific variety in the valley. The fruit is mostly sold to large producers like Kendall-Jackson for their California blends.
After Chardonnay, there are more acres of Gewürztraminer planted in Santa Clara County than all other white varieties combined. Almost all those vines are in the Dunne Ranch vineyard too.
At over 100 acres, Ridge's Monte Bello vineyards are the largest in the Santa Cruz Mountains AVA, but are only 6th overall in Santa Clara County.
The Wineries of Santa Clara Valley is an organization representing many local wineries. This weekend is their twice-yearly Passport event; a passport costs $30 and gives you entrance to 25 different wineries.
1The plaque reads: On this site, in 1852, Charles LeFranc made the first commercial planting of fine European wine grapes in Santa Clara County to found Almaden Vineyards. LeFranc imported cuttings from vines in the celebrated wine districts of his native France, shipping them by sailing ship around the Horn. This is incorrect, as outlined above.