Santa Margarita Ranch is an AVA established in 2014 as one of 11 specific designated sites within the wider Paso Robles viticultural area on California's Central Coast. Santa Margarita is the southernmost of the Paso Robles sub-regions and is the only territory not adjacent to any other AVAs. It takes its name from a historic Spanish mission built in the region as an outpost for the greater Mission San Luis Obispo de Tolosa, with the lands around the outpost being known as "Santa Margarita Rancho".
The region of Santa Margarita Ranch mostly encompasses a valley floor surrounded by hills ascending to higher elevations. On its eastern border it follows the Salinas River, and on its western border it is flanked by the Santa Lucia Range. Much of its border lines up with the most southerly boundaries of the greater Paso Robles viticultural area. The exception is in the southwest where it skirts the Los Padres National Forest where commercial viticulture is restricted.
Elevations range from 900 to 1400 feet (272-426m), with the majority of vineyards being located on the valley floor. Santa Margarita is too far south to be affected by the Templeton Gap, but cool ocean breezes do enter through the Cuesta Pass, a more southerly series of gaps in the peaks of the Santa Lucia Range. The overall marine influences on the valley are modest, but it still has the high annual rainfall average of 29 inches. Santa Margarita is capable of warmer days and cooler nights than other regions of Paso Robles, though cold air draining from higher elevations can pool making frost a serious concern for growers.
The soils consist of young sandy loams on the valley floor with more gravel content at higher elevations. The major grapes are similar to other Paso Robles regions with Syrah and other Rhône varieties being well represented.
