“We hear from people all the time who are surprised to learn that Monte Bello is not from Napa Valley,” Mr. Draper said during a recent visit to Ridge’s hilltop winery near Cupertino.

Today, the cabernet sauvignon produced in the region is among America’s best, particularly for fans of classically structured, savory wines, and is certainly among the best cabernet values. Yet only small amounts are produced, and that amount is unlikely to grow anytime soon.

The appellation is the rare wine region defined by elevation. In the hills south of San Francisco, including land in three counties from Woodside and Menlo Park on the north to Santa Cruz and Watsonville on the south, the vineyards must largely be above the fog line, from about 800 to 2,700 feet. The region also encompasses the boundary between the Pacific and North American tectonic plates. The San Andreas Fault passes through.

Paul Draper, Ridge's CEO and head winemaker, visits the UK, Ridge's most important export market, at least once a year, but also travels widely in the rest of Europe. What may help Ridge wines' appeal to the British, apart from the relatively moderate pricing, is Ridge's steadfast adherence to traditional winemaking techniques and a style that is unashamedly modelled on that of the Bordeaux first growths, with the twist that Draper and team favour well-seasoned American oak above barrels imported from France.