The Moon Mountain District Sonoma County AVA was approved on October 1, 2013. It’s a feather-shaped region that runs northwest to southeast and comprises roughly 17,663 acres overall, 1,500 acres planted to wine grapes—including some very old and respected vineyards. The appellation is enclosed entirely within the already existing Sonoma Valley AVA, but is very distinct by virtue of its soils and altitude.

A view from Hanzell Vineyards. Photo: Hanzell Vineyards

The Moon Mountain District Sonoma County AVA lies on the west side of the Mayacamas mountains. [The ridge line of that range serves as the dividing line for Sonoma and Napa Counties, as well as their respective AVAs.] Altitude in the new AVA rises from 400 to 2,200 feet. Severity of the slope varies but the terrain is generally similar to that of it’s eastern neighbor, the Mt. Veeder AVA, though the latter faces east rather than west.

Origins of the Name “Moon Mountain”

The Moon Mountain District Sonoma County is named for a particular peak within the range. The appellation is broader than just one peak though and there are Moon Mountains in nine other states, so it was decided to go with “Moon Mountain District Sonoma County.” Surprisingly, the mountain itself only received that name in 2007.

“Valley of the Moon,” a name made famous by the writer Jack London among others, is the literal translation of “Sonoma” from the language of the local Pomo and Miwok tribes. There have long been local businesses whose names include Valley of the Moon and some, located in the hills, referred to Moon Mountain. This was due, in part, to the renaming of a nearby road from Goldstein Road to Moon Mountain Drive in 1957. Fifty years later, it was decided that given the name of the road and those businesses, there ought to be an actual Moon Mountain too.

The Soils

Mountain growing areas tend to differ substantially from those on a valley floor. Soils are thinner on the mountains, due to erosion, and the slopes encourage water drainage. Altitude can also affect climate with high vineyards often being above the fog line. Attitude toward the sun, hence hours of direct sunlight, and the amount of rainfall also differ. This is all true for Moon Mountain District Sonoma County, justifying the creation of this new AVA.

One of the things that makes the wine-growing areas of Napa and Sonoma Counties so complex is their jumble of soils. The Mayacamas Range exemplifies this. It’s soil is largely a range of sedimentary materials—former sea floor—pushed up and exposed eons ago during two major and long-lasting land formation events driven by movement of tectonic plates. Moon Mountain District Sonoma County soils, however, are largely volcanic. Some of this distinctive soil, deep red from plentiful iron, inspired the name of its most celebrated vineyard, Monte Rosso. The soil distinguishes the new AVA from those neighboring it.

The Climate

The Moon Mountain District Sonoma County AVA, like most in California, has a Mediterranean climate which means long dry summers and moderate winters during which most of the year’s rain falls. The AVA is cooled somewhat by breezes from both the Pacific Ocean and San Pablo Bay though its distance from each limits their influence. Altitude results in long, bright days in the new appellation and its western facing means full exposure to the intense afternoon sun. Achieving ripeness there for wine grapes is almost never a problem.

The Wine Styles

The wines for which Moon Mountain District Sonoma County AVA is best known are ripe, richly-fruity Cabernet Sauvignon and Zinfandel. The most iconic vineyard is Monte Rosso with it’s 123-year old Zinfandel and 75-year old Cabernet Sauvignon vines. It’s also the vineyard which inspired Frank Schoonmaker and Louis M. Martini to first use the term “mountain wine” on a California wine label.

Monte Rosso is not the AVA’s only landmark vineyard though. Hanzell Vineyards straddles the Mayacamas ridge at the southern end of Moon Mountain District Sonoma County. There, closer proximity to San Pablo Bay and some eastern exposures allow for structured and eminently age-worthy Chardonnay and Pinot Noir. Hanzell’s Ambassador’s 1953 Vineyard also includes the oldest continuously producing Chardonnay and Pinot Noir vines in the United States.

Morgan Twain-Peterson of Bedrock Vineyards talks about the Monte Rosso Vineyard:

Moon Mountain District Sonoma County AVA Details

Latitude: 38.3 degrees

Elevation: 200-2,200 feet

Climate: Mediterranean

Average Growing Degree Days: 2,900 – 3,400

Winkler Classification Region: high II to moderate III

Annual Rainfall: ~ 30 inches

Soils: shallow and well-drained volcanic (dark brown and red, plus rhyolitic tuff)

Total Acres: 17,633

Vineyard Acres: about 1,500

Wineries: 4

Primary Red Grape Varieties: Cabernet Sauvignon, Pinot Noir (Hanzell), Syrah and Zinfandel

Primary White Grape Varieties: Chardonnay

A Selection of Significant Vineyards and Wineries

Amapola Creek (four vineyards)
B Wise Vineyards
Caton Vineyard (Ty Caton Vineyards)
Hanzell Vineyards
Kamen Estate
Kistler Vineyard
Liquid Sky
Lookout Ridge
Monte Rosso Vineyard (owned by Louis M. Martini, now part of Gallo)
Moon Mountain Vineyard & Repris
Petroni Vineyards
Rattlesnake Ridge (J. Baldwin Wines)

Copyright Fred Swan 2013. Video copyright Bedrock Vineyards. Map courtesy of Sonoma County Vintners. All rights reserved.