Clarksburg is an American Viticultural Area (AVA) in California's Sacramento Valley spanning across portions of Sacramento, Solano and Yolo Counties. Lying southwest of the state capital of Sacramento, the wine appellation was established as the nation's 57th and the state's 37th AVA on January 23, 1984, by the Bureau of Alcohol, Tobacco and Firearms (ATF), Treasury after reviewing the petition submitted by John Baranek of Clarksburg Vintners & Growers proposing the viticultural area within Yolo, Solano and Sacramento Counties known as "Clarksburg."
The sixteen-mile-long (26 km) by eight-mile-wide (13 km) viticultural area encompasses 64,640 acres (101 sq mi) and named after the town of Clarksburg, located in its northern section. The growing region has dense clay, silt, and loam soils. Fog and cool breezes from San Francisco Bay keeps Clarksburg AVA cooler than Sacramento. At the outset, Clarksburg contained two bonded wineries and 25 vineyards cultivating approximately 10,000 acres (4,000 ha) of Vitis vinifera. While the Clarksburg appellation produces over 40,000 tons of grapes annually, 90% of the grapes grown in the AVA are processed in winery facilities located elsewhere in California, and relatively few wines are released with the Clarksburg AVA on their labels. The established Merritt Island viticultural area became a sub-appellation within Clarksburg AVA. The plant hardiness zone is 9b.
In 2022, the Alcohol and Tobacco Tax and Trade Bureau (TTB) approved the petition submitted by James Reamer of Reamer Farms Vineyard, on behalf of himself and other wine industry members, to expand the Clarksburg viticultural area by approximately 27,945 acres (44 sq mi) in Sacramento and Solano counties totaling 92,585 acres (145 sq mi). The expansion area was adjacent to the AVA's southern boundary entirely encompassing both Grand and Ryer Islands which defined the added acreage. There was 350 acres (140 ha) being cultivated on Grand Island and three vineyards on Ryer Island. The soil, climate, topography and hardiness zone in the expansion area are similar to the established Clarksburg AVA.