[3] The AVA is situated at the northernmost portion of the Paso Robles viticultural area along the San Luis Obispo–Monterey County border where the Salinas River flows across northbound toward the Pacific Ocean into Monterey Bay.
The viticultural area has a very mild marine influence, receives an average annual precipitation of 11.4 inches (290 mm), and is considered a warm Winkler Region III climate zone.
The expedition reported surveying a large region, from the Nacimiento River to the Arroyo de Santa Ysabel, and for several miles on either side.
[6] Franciscan Mission San Miguel Arcángel was dedicated on July 25, 1797, and construction began with the help of the local native population, the Salinan tribe.
The extent of these lands was given in a report made by Father Juan Cabot in 1827:[5]From the mission to the beach the land consists almost entirely of mountain ridges... for this reason it is not occupied until it reaches the coast where the mission has a house of adobe... eight hundred cattle, some tame horses and breeding mares are kept at said rancho, which is called San Simeon.
After the Mexican secularization act of 1833, the property was sold in 1846 by the last Alta California governor, Pio Pico, for $600 to Petronillo Rios and William Reed.
The monotony of affairs was somewhat shaken in 1881, when the engineers of the Atlantic and Pacific Railway arrived in the vicinity of San Miguel and set their stakes, preliminary to the actual work of building a railroad.
[10]The Southern Pacific Railroad reached San Miguel in 1886 giving ranchers and farmers direct access to the markets to the north.
After World War II, with the departure of most of the soldiers from Camp Roberts, San Miguel lost a large portion of its economic base.
Camp Roberts briefly returned to active status during the Korean War and for a time San Miguel flourished once more.
[11] The earliest vine plantings in the Paso Robles area can be traced back to the missionaries of Mission San Miguel Arcángel.
Father Junípero Serra planted more than a thousand vines and produced wine for sacramental purposes and brandy for export.
In the 80s, David Caparone, after extensive research on clonal types and microclimates, decided to pioneer an experimental Nebbiolo vineyard in the San Miguel area.
[13][14] The "San Miguel" name also has been used in association with various historical and modern community districts located within the boundary of the viticultural area.
However, the boundary was amended at TTB’s request to exclude land within Camp Roberts Military Reservation from the viticultural area since it is unavailable for private use.
[2][5] Both the Salinas and Estrella Rivers bisect the San Miguel District viticultural area, and they converge near the center of the region.
The highest elevation in the San Miguel District viticultural area is an approximately 1,600 feet (490 m) peak located near the northern portion of the boundary, according to the USGS maps.
The region to the north, which is part of the Temblor Range, contains steep canyons and mountainous terrain that contrast to the low elevations, river terraces, and footslopes of the viticultural area.
The San Miguel weather station averages 11.4 in (290 mm) of annual precipitation; this low level is largely a function of the rain shadow created by the Santa Lucia Range to the west of the viticultural area.
The San Miguel District viticultural area has a Winkler Region III climate, with 3,300 to 3,400 annual GDD unit totals, based on anecdotal evidence from local growers and intermittent weather data.
Mollisols dominate the soil orders of the San Miguel District viticultural area, but older Alfisols and Vertisols are also present.
Numerous wineries have produced highly-acclaimed wines from his head-trained[15], dry-farmed Zinfandel vineyard in the San Miguel District.
San Miguel's predominant grape varieties are congruent with the greater Paso Robles viticultural area with its red wines led by Cabernet Sauvignon and Merlot.