The second-largest of the new appellations is the 14,000-acre High Valley AVA, in the eastern portion of California's Lake County, about 85 miles north of San Francisco. The valley, 9 miles long and 3 miles wide, is nestled in the mountains above Clear Lake's northeastern shores and ranges in elevation from about 1,700 feet to above 3,000 feet. The valley's east-west orientation pulls in cool marine air, making the temperature generally lower than in the rest of Lake County's growing regions. Its soils are alluvial, red volcanic cinders and pumicelike gravel and stones.

About 1,000 acres of vineyards are planted in High Valley. Red varieties such as Cabernet Sauvignon, Syrah, Zinfandel, Merlot, Petite Sirah and Tempranillo are grown on the ridges, while cooler-weather varieties such as Sauvignon Blanc, Pinot Grigio and Pinot Noir are grown on the valley floor. High Valley's winegrowing history dates to the 19th century, but during Prohibition, the vines were replaced with other agricultural crops. New wineries have since sprung up, including Shannon Ridge, Brassfield Estate Winery (which submitted the AVA petition), Monte Lago and High Valley Vineyard.