California's Sonoma Valley is arguably America's second most famous wine region. It is trumped only by the Napa Valley, its eastern neighbor on the other side of the Mayacamas Mountains. It should be noted, however, that it is the name 'Sonoma' that has gained this fame, rather than the Sonoma Valley per se. While the term 'Napa' essentially covers all wines from Napa County and Napa Valley, 'Sonoma County' and 'Sonoma Valley' are far from synonymous. This distinction is vital to those seeking an understanding of California's two top wine regions.
The Sonoma Valley AVA covers a long, thin tranche of Sonoma County's south-eastern corner and is entirely separate from the prestigious AVAs of Northern Sonoma, which include the likes of Russian River Valley, Alexander Valley and Knights Valley. Santa Rosa town, at the northern end of the valley, marks the transition between these two areas. The valley lies between the Mayacamas and Sonoma mountains and is drained by Sonoma Creek, one of Sonoma County's two key rivers (the other being the much longer Russian River). Sonoma Creek rises on Sugarloaf Ridge in the Mayacamas and flows southwards for roughly 35 miles (60km) before discharging into San Pablo Bay. Sonoma Valley follows the creek for its entire length.
Within the north-western third of the Sonoma Valley AVA lie the Sonoma Mountain AVA and its lower-lying neighbor Bennett Valley. While they produce a handful of interesting wines, these two small AVAs are far from famous. The story is quite different at the southern end of the valley, where it crosses over into the famous Carneros AVA. Carneros (or Los Carneros) is divided roughly in half between Sonoma and Napa and represents the meeting point between the two valleys. It is widely regarded as the source of California's finest Pinot Noir and Chardonnay wines, meaning that almost all wines from this part of the valley use the Carneros title instead of the Sonoma Valley name, to which they also have a right.
The wines for which Sonoma Valley is known are rich reds made from Cabernet Sauvignon, Zinfandel and ripe, generously flavored (and generally oaked) Chardonnay. The occasional Sonoma Valley Merlot is also to be found on the market, although these have been increasingly rare since the variety's fall from favor in the 1990s. That said, some producers – notably Chateau St Jean right at the northern end of the valley – have stood by their Sonoma Valley Merlot.
The very first vineyards here were established in the late 1850s, at around the same time that George C. Yount began making Napa Valley wines just over the Mayacamas. Buena Vista and Gundlach Bundschu wineries, on the eastern outskirts of Sonoma town, were established in 1857 and 1858 respectively.