California is the United States of America's largest and most important wine region. It produces 90% of the USA's total production - with the fair majority of that being red wines. Since it is 'always sunny in California' it is the perfect region to grow red grapes that need a lot of heat to ripen up. This has lead to Cabernet Sauvignon, Merlot and an Italian grape varietal: Primitivo (Californian's call in Zinfandel) to being the most important red grapes. Chardonnay is the leading white followed by Sauvignon Blanc.