A large AVA, San Francisco Bay covers an area of more than six-hundred-thousand hectares, stretching from the cosmopolitan metropolis of San Francisco to the southern tip of the Santa Clara Valley. It encompasses the counties of [Alameda](/county/alameda-county), [Contra Costa](/county/contra-costa-county), Santa Clara, San Francisco and San Mateo, as well as parts of [Santa Cruz](/county/santa-cruz-county) and [San Benito](/county/san-benito-county), and includes important smaller viticultural areas such as the [Santa Cruz Mountains](/ava/santa-cruz-mountains-ava) and [Livermore Valley](/ava/livermore-valley-ava) AVAs. Like much of the state of [California](/region/california), the wine history of San Francisco Bay began around the time of the gold rush (1848), when huge numbers of people - from the eastern states - and more significantly, from a host of European nations, flooded west in search of their fortune. European Vitis Vinifera varieties were subsequently planted in the area - particularly along the Santa Clara Valley - and growth remained steady until prohibition curtailed development in the 1920s. The AVA and the state in general has however seen something of a remarkable revival over the last half century, producing wines that can compete with the very best of the Old World. The microclimates of this area are all - to varying degrees - influenced by the Pacific Ocean breeze and the fog that rolls in off the cool waters of the bay, moderating the warmer temperatures and ensuring an extended ripening season for the AVAs grapes. The fruits here are therefore well balanced and flavoursome, whilst their natural acidity is also preserved. Factors such as elevation, aspect and soil composition vary across the smaller AVAs that make up this larger viticultural area; from deep, sandy soils to gravel, from high altitude plots to low lying vineyards, the terroir of San Francisco Bay is as broad and varied as the wines it delivers.