The Clear Lake appellation -- just north of Sonoma and Napa counties and east of Mendocino -- contains the largest body of fresh water in California. The lake acts as a temperature moderator and covers half the surface area of this viticultural region. Uniformly cooler than any northern California appellation, Clear Lake AVA has become well known for its Sauvignon Blanc in recent years. However, the lake also causes viticulturalists a good amount of stress as it has a tendency to flood during rainy seasons. Before Prohibition, this area had over 5,000 acres of vineyards and 36 wineries. Without brand recognition, none of them survived into the mid-20th century. Understandably, local winemakers wish to avoid a repeat of this phenomenon and therefore actively promote the appellation name on labels.