Santa Maria Valley is an American Viticultural Area (AVA) which straddles the boundary of Santa Barbara and San Luis Obispo counties in California's multi-county Central Coast AVA. It was established on August 5, 1981, by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) as California's second oldest AVA. A portion of the AVA crosses the Cuyama River into the southernmost corner of San Luis Obispo County. The east-west orientation of the 152.3 square miles (97,483 acres) with a wide, open valley and rolling hills means cool winds and fog flow in freely from the Pacific Ocean, settling most noticeably in lower-lying areas. The result is a mild Mediterranean climate that lengthens the growing season and contributes to the eventual sugar/acid balance in the grapes from Santa Maria Valley's 7,500 acres (3,000 ha) cultivated vineyards. On January 28, 2011, the AVA was granted a 29.4 square miles (18,790 acres) expansion to its southern boundary.

Santa Maria Valley has a rich viticulture history in California. Grape-growing in the region dates back to the Mexican Colonial period of the 1830s. Modern viticulture in the Santa Maria Valley dates back to 1964 when more than 100 acres of vineyards were planted in the Santa Maria Valley. The new growers believed the area could grow wine grapes to rival the Napa Valley. By the mid-1970s, established vineyards increased cultivation to over 2,000 acres (810 ha).

The Santa Maria Valley is a natural funnel-shaped valley opening west to the Pacific Ocean. The elevation of the area ranges from approximately 200 feet (60 m) at the intersection of Highway 101 and the Santa Maria River to approximately 3,200 feet (980 m) at Tepusquet Peak. The grapes that are grown within the area are on the valley floor at an approximate elevation of 300 feet (90 m) and on the slopes and rolling hillsides up to an elevation of 800 feet (240 m).

Santa Maria, California
Climate chart (explanation)
J F M A M J J A S O N D     3.1     64 39     3.5     65 41     3.2     66 43     1     69 44     0.3     71 47     0.1     74 50     0.1     77 52     0.1     78 53     0.3     78 52     0.5     76 48     1.4     70 43     2.1     64 38 █ Average max. and min. temperatures in °F █ Precipitation totals in inches
Metric conversion J F M A M J J A S O N D     79     18 4     89     18 5     81     19 6     25     21 7     7.6     22 8     2.5     23 10     2.5     25 11     2.5     26 12     7.6     26 11     13     24 9     36     21 6     53     18 3 █ Average max. and min. temperatures in °C █ Precipitation totals in mm

The Santa Maria Valley geography channels dense banks of morning fog from the Pacific Ocean that takes many hours to burn off, only to be replaced by chilly afternoon breezes. This “maritime fringe” climate lengthens the growing season and contributes to the eventual sugar/acid balance in the grapes from the region. Summer in the Santa Maria Valley is goose-bump season, with an average summer temperature of only 75 °F (24 °C). This is a growing environment that is a Region I on the Winkler Scale. As with most of Santa Barbara County, annual rainfall is very low in the Santa Maria Valley. The AVA averages less than 14 inches (360 mm) in non-drought years. Vines typically require 20–30 inches (510–760 mm) of water per year for dry-farming, therefore, irrigation is essential.

The soils range in texture from sandy loam to clay loam and are free from adverse salts. Soil variation can be broadly categorized into four types. Three types are within the original Santa Maria Valley AVA: the Valley floor, the Solomon Hills, and the foothills of the Sierra Madre Mountains, northeast of the Santa Maria River. The fourth is the southern expansion area. Along the northern portion of the Santa Maria-Sisquoc River colluvial soils cover slope sides giving rocky freshness to grapes grown throughout. Towards the river side, soils become unconsolidated as mixed alluvial soils appear. The soils are mainly sand, sandy loam, and loam on the valley floor, but are mixed sandy, clay, shaly, and silt loams on mountain slopes. However, the soils in the expansion area are the same type as in the original Santa Maria Valley area. In the expansion area and on hills in the original viticultural area, the soils are sand, sandy, clay, and shaly loams.

Due to the cooler mesoclimates, the valley is renowned for producing some of California's finest Pinot Noir and Chardonnay wines. These are the appellation's two flagship varieties.

On January 28, 2011, the TTB granted a petition to expand the southern border of the Santa Maria Valley American Viticultural Area (AVA). This expansion was intended to align with the physical watershed boundary of the Santa Maria River. The revised boundary approximately follows the ridge line dividing the Santa Maria Valley from the Los Alamos Valley. It lies in northern Santa Barbara County, according to the boundary description and USGS maps, and is entirely within the Central Coast viticultural area. The expansion added 18,790 acres (7,600 ha), nine vineyards, 255 acres (103 ha) of commercial viticulture, and 60–200 acres (24–81 ha) under viticultural development to the area increasing its total size to 116,273 acres (47,054 ha).

• Santa Maria Valley Santa Barbara Vintners Association
• TTB AVA Map

34°51′15″N 120°15′42″W / 34.85413°N 120.26163°W / 34.85413; -120.26163