Equidistant from the town of Calistoga to the south and [Clear Lake](/ava/clear-lake-ava) to the north, Guenoc Valley covers an area of one-thousand-eight-hundred hectares, and has a long history of winemaking dating back to the 1880s. It was then that the [British](/country/united-kingdom) stage actress Lillie Langtry was the first to recognise the area's potential for quality viticultural activity, and subsequently established vineyards and a winery in this idyllic southern portion of [Lake County](/county/lake-county). Guenoc Winery - now named [Langtry Estate](/producer/langtry-estate-vineyards) in honour of its founder and former proprietor - remains the appellation’s only cellar, producing acclaimed, 100% estate grown wines from a number of key varieties. One of [California's](/region/california) warmest terroirs, Guenoc Valley is sheltered from the cooling influence of the Pacific Ocean by the imposing Mayacama Mountains. As a result, elevation - and its moderating effect on temperature - is integral to the success of Guenoc Valley grapes. Planted on ridges at altitudes of four-hundred plus metres above sea level, the vines here are blessed with abundant daytime sunshine and high diurnal temperature variation, delivering grapes of great intensity and perfect balance. Given the often extreme heat during summer and the inherent risk of over-ripening, Guenoc Valley grapes are often amongst the first in the county to be harvested. With a similar geology and topography to that of nearby [Red Hills AVA](/ava/red-hills-ava), the steep, mountainous terrain and rocky, volcanic soils that drain freely, are conducive to the production of concentrated, low yielding, premium wines. In addition to the aforementioned varietals, Guenoc Valley growers also cultivate [Petite Sirah](/petite-sirah), [Syrah](/syrah), [Merlot](/merlot) and [Zinfandel](/zinfandel) amongst others.