An American Viticultural Area, or AVA, is defined as a vineyard zone classified based on geography and climate. The purpose of AVAs is to showcase unique soil types, unique microclimates, and unique conditions for grapes.

Recently, the Wine History Project created a project within our archival files for information about the American Viticultural Areas, or AVAs of San Luis Obispo County. We are calling it The AVA Project. Original, right? The objective is to do four things:

  • identify each one of these AVAs in SLO County, 
  • document unique information for each AVA by creating spreadsheets which categorically identify these acquired facts, 
  • maintain (or create) maps that would be available for reference and article purposes, and,
  • help to share the history of the AVAs themselves with the public.  

To start out, let me explain that San Luis Obispo County has a total of five American Viticultural Areas, or AVAs, with an additional eleven sub-appellations or districts. That adds up to a total of sixteen different areas in the county that have been identified to be helpful to the wine customers or visitors. AVAs help to assist them with finding the type of terroir, climate, grapes, and wine they are looking to taste and then explore or learn more about.

American Viticultural Areas in San Luis Obispo County include:
Edna Valley AVA established 1982, amended 1987
Paso Robles AVA established 1983
York Mountain AVA established 1983, amended 1987
Arroyo Grande AVA established 1990
San Luis Obispo Coast AVA established 2022

According to the Alcohol and Tobacco Tax and Trade Bureau, or the TTB website (,  “any interested individual or group may petition TTB to establish a new AVA or modify an existing AVA. The complete process for creating and submitting a petition is outlined in their regulations.”


The AVA Project Historical Objectives 

The Wine History Project of San Luis Obispo County’s objective will be to archive the historic maps, letters, original petitions, and documents which were created and led up to some of the collaborative efforts to petition to establish our county’s viticultural areas known as AVAs.

Our approach to this project was first to research local information, both written and verbal, for the past forty years. From this initial research we will start the process of creating spreadsheets of information obtained. The spreadsheets will have limited facts but we believe that the archival of this information will lead to personal and privately held paperwork by members of the San Luis Obispo County community. 

Here is a list of categories to be documented on these spreadsheets:

  • Date the area originally established in the county
  • Date the AVA was established
  • Vineyard acres planted by 2022
  • Notable history of area
  • Primary grape varieties
  • Terroir description
  • Climate
  • Other miscellaneous information
  • Wineries

To demonstrate this, I have utilized research found in Paso Robles AVA historical information created initially in the petition written in July 26, 1982 submitted to the Department of the Treasury Bureau of Alcohol, Tobacco and Firearms, in Washington, D.C. along with some information from a blog written from March  2020 to October 2021 by Christopher (Chris) Taranto, the Communications Director of the Paso Robles Wine Country Alliance since 2007. And to continue, future information will make use of the additional research done by Larry Roberts and Carol Manning for the California Central Coast Wine Growers Association (CCWGA) along with WHP interviews with Gary Eberle, Noreen Martin, Victor Hugo Roberts and July Ackerman.

These major records, along with a variety of information from local winemakers, internet resources, and historical data from books and various newspaper and magazine articles throughout the years have been used as my starting point.

Much work and research will need to be done to obtain a fruitful and complete provenance on this topic. We will continue to update you on our progress of this information. 

An example of what information is started for the spreadsheet on the Paso Robles AVA.

Date the Area Originally Established in SLO County

City of Paso Robles was founded in 1889. It has an important agricultural history.

Date the AVA Established

A letter was sent to the Director of the Department of the Treasury Bureau of Alcohol, Tobacco and Firearms on July 26, 1982 on letterhead from the Martin Brothers Winery. 


An early label from their famous Nebbiolo prior to the AVA designation

The letter states, “This petition is a joint and collaborative effort of the wineries and winegrowers in the proposed area.” It continues, “The unanamity (sic) of fourteen wineries and the grape growers of over 3,800 acres in the proposed area express the favorable opinion of nearly 100% of all those affected by the appellation”. 

Included are documents, known as exhibits, to substantiate the criteria to seek approval of the appellation. The AVA was approved in 1983; which was large to accommodate all the existing vineyards and wineries at the time. 

These documents now reside in the Paso Robles “file” of our WHP electronic archives.

Vineyard Acres Planted With Wine Grapes as of  2022

According to an article dated July 15, 2022, by the Wine Industry Advisor (  ) Paso Robles Wine Country is California’s third-largest wine region and encompasses more than 40,000 vineyard acres and 200 wineries.

Notable History of Area

In 1981 the California Central Coast Wine Growers Association published the following list of 13 wineries in what became the Paso Robles Appellation.

Caparone Winery, Estrella River Winery, HMR, Las Tablas Winery, Mastantuono Winery, Pesenti Winery, Ranchita Oaks Winery, York Mountain, El Paso De Robles, Fairview Farm Vineyard, Martin & MacFarlane Winery, Old Casteel Vineyard, and Tobias Vineyard. 

In 2022, more than 200 wineries in Paso Robles AVA exist. The Paso Robles AVA is part of the California Central Coast AVA.  The area is situated on the inland side of the Santa Lucia Coastal Mountains in San Luis Obispo County. It is a rectangular shaped area approximately 35 miles wide by 25 miles long in northern San Luis Obispo County.

Primary Grape Varieties

Today there are over 50 grape varieties planted. The heritage grape is Zinfandel, first planted in the second half of the 19th century. After Prohibition, other grape varieties were slowly re-introduced in the North County.

The agricultural advisor, Jack Foott, planted experimental vineyards with Pinot Noir, Pinot Chardonnay, Cabernet Sauvignon, and Riesling throughout the county in the 1960s. He assisted growers in selecting the varieties most likely to thrive in each vineyard.

In the late 1960s, large commercial growers planted vineyards with irrigation, selling grapes to winemakers throughout California. Zinfandel, Cabernet Sauvignon, and Chardonnay were in demand as the California Wine Revolution took hold. Italian varieties were researched and planted in the 1980s. Rhone varieties were widely planted in the 1990s. 

Terroir Description

In this giant AVA there are over 45 different soil series, including – granite, sedimentary, volcanic, sandstone, and the largest Calcareous based soil formation in all of California. Some soils are clay-based with high lime content which produces higher pH levels. Other soils are primarily bedrock, composed of weathered granite, volcanic and marine sedimentary rocks overlayed with sandstone, mudstone or calcareous shales.


Paso Robles AVA has warm weather. Paso Robles is known for its heat during the day time and cool weather at night. Average daytime temperature in the growing season can reach 105 degrees/Fahrenheit. Night temperatures drop by 40-50 degrees/Fahrenheit. The area is close to the Pacific Ocean which accounts for the fog, breezes, and temperatures. Rainfall levels vary from desert-like 10 inches/year up to 40 inches in the higher elevation regions. Elevation starts around 700 feet in the east and reaches up to 2400 feet on the west side of the Paso Robles AVA.

Additional Miscellaneous Information

By 1996 many more vineyards, grape varieties, and wineries were established.

There was a great focus on marketing and making Paso Robles a tourist destination. Hotels and restaurants were established. Many wineries established tasting rooms and wine clubs to sell their wines.    

In 2007 a conjunctive labeling law (AB87) was passed, which preserved brand awareness of the Paso Robles AVA. This meant that the Paso Robles AVA and the designated districts(s) would appear together on any wine label. In 2009, this proposal was withdrawn. 

In 2014, the U.S. Alcohol and Tobacco Tax and Trade Bureau issued a final rule in the Federal Register which established 11 new District AVAs within the existing Paso Robles American Viticultural Area.

Each of the sub-appellations, or districts of the Paso Robles AVA have differing information which will be detailed and shared within their own spreadsheets at a later writing. These sub-appellations include:

Adelaida District AVA established 2014
Creston District AVA established 2014
El Pomar District AVA established 2014
Paso Robles Estrella District AVA established 2014
Paso Robles Geneseo District AVA established 2014
Paso Robles Highlands District AVA established 2014
San Juan Creek District AVA established 2014
San Miguel District AVA established 2014
Santa Margarita District AVA established 2014
Templeton Gap District AVA established 2014
Paso Robles Willow Creek District AVA established 2014


Currently, there are over 200 in the Paso Robles area.

In Addition…

The Wine History Project has a large collection of artifacts used during the 19th and 20th centuries in the vineyards and for winemaking. If you wish to make a donation to our collection, or have documented information or personal stories regarding the AVAs, please contact Cindy Lambert at