One Estate.

Trefethen Vineyards is located in The Oak Knoll District of Napa Valley American Viticultural Area, which lies between the small town of Yountville to the north and the city of Napa to the south. Its 3,500 vine acres are planted to 18 classic vinifera grape varieties, making OKD Napa Valley's most diverse appellation.

Established in 2002 thanks in large part to the efforts of Janet Trefethen, the Oak Knoll District is located at the southern end of the Napa Valley. Its name stems from the Oak Knoll Ranch that was quite well known in the mid-1800s. It is one of the coolest areas in the Napa Valley. This climate allows some parts of the Oak Knoll District to excel with cooler weather grapes like Pinot Noir and Chardonnay. Other portions succeed with Cabernet Sauvignon and Merlot.

The district's soils derive from the large Dry Creek alluvial fan, while its climate defines a sweet spot between Napa's warmer up-valley appellations and its cool southern tip. Morning fog and cooling afternoon breezes from San Pablo Bay regulate the ripening process and help support a broad range of varietals ranging from Riesling to Cabernet Sauvignon.

OKD is one of the rare spots in Napa Valley both warm enough to ripen Cabernet Sauvignon and Merlot and cool enough to provide an ideal environment for Chardonnay. The strong marine influence results in cooler temperatures and higher humidity than in other Napa growing districts, preserving the bright aromas and flavors for which OKD grapes and wines are celebrated.

Other benefits of the appellation include lower winter and spring rainfall totals, resulting in warmer soils early in the growing season; lower summer temperatures, extending the ripening season and harvest period; and longer grape hang times, enabling OKD fruit to develop concentrated flavors at moderate sugar levels with good balancing acidity.