Santa Clara Valley is an American Viticultural Area (AVA) located mostly in Santa Clara County, California. The area served an important role in the early history of California wine and was home to the pioneer winemakers Paul Masson and Charles Lefranc. It was established on April 27, 1989 by the Bureau of Alcohol, Tobacco and Firearms (ATF), Treasury after evaluating the petition proposing a viticultural area in Santa Clara, San Benito, San Mateo and Alameda Counties that extends from lower San Francisco Bay with the cities of San Jose, Santa Clara, Menlo Park, Mountain View and Fremont toward the southern boundary near Gilroy and Morgan Hill, outlining the viticultural area named "Santa Clara Valley." It includes the historic winegrowing areas of Santa Clara County not already within the [Santa Cruz Mountains viticultural area, plus the area near Mission San José in Alameda County and a small part of San Benito County. Santa Clara Valley encompasses the established viticultural areas, Pacheco Pass and San Ysidro District.