The viticultural history of Oak Knoll reflects that of the wider region with the first vines planted here soon after the gold rush and the initial success of the industry thwarted in the early twentieth century by Phylloxera and Prohibition. The second wave of winemaking across [California](/region/california) began in the 1960s; for Oak Knoll this started when the Trefethen family (of Trefethen Vineyards) reclaimed land in the area which had been neglected since the onset of Prohibition. Twenty-five kilometres to the north of San Pablo Bay, Oak Knoll’s climate is heavily influenced by the cooling fog and marine air which often lingers into the early afternoon. In combination with the frequent ocean breezes travelling up the valley, this creates temperatures a few degrees lower than more northerly appellations such as [Calistoga](/ava/calistoga-ava) and [St Helena](/ava/st-helena-ava), extending the growing season to ensure grapes which are complex, rich in flavour and naturally acidic. The geology of Oak Knoll is dominated by the Dry Creek alluvial fan and free draining soils of sand, gravel and clay which force the roots deep in search of nutrients, complete a unique terroir. Today, the appellation covers a geographic area of three-thousand-four-hundred hectares of which around half is planted to vine. The unique conditions here enable almost twenty different varieties to thrive in the vineyards. [Cabernet Sauvignon](/cabernet-sauvignon) and [Chardonnay](/chardonnay) are the principal grapes of each type, whilst others with significant plantings include [Bordeaux](/region/bordeaux) red grapes [Merlot](/merlot), [Cabernet Franc](/cabernet-franc) and [Malbec](/malbec) as well as [Zinfandel](/zinfandel), [Syrah](/syrah), [Sauvignon Blanc](/sauvignon-blanc) and [Pinot Noir](/pinot-noir). Although not quite held in the same regard as the similarly named [Oakville AVA](/ava/oakville-ava), Oak Knoll District’s winemakers continue to enhance the reputation of the appellation’s terroir and its subsequent wines. Elegant, well-balanced red wines with flavours of dark fruits and tobacco are the standard, whilst [Chardonnay](/chardonnay) varietals tend to be crisp and aromatic with a fresh acidity. Evidently, Oak Knoll is an AVA on an upward curve towards the very top.