Why Contra Costa Sandy Soil Grows Grapes Winemakers Fight Over
There’s a reason serious winemakers from the Bay Area and beyond have been quietly sourcing grapes from eastern Contra Costa County for years. It’s not a trend. It’s the ground. Here’s what makes this corner of California so good for growing wine grapes — and how to get the fruit, or the wine, from our family vineyard in Knightsen.
A corner of California most people drive past
Contra Costa County sits directly east of San Francisco Bay — about 50 miles from the city, past the suburbs, out where the land flattens and opens up toward the Sacramento Delta. Towns like Brentwood, Oakley, and Knightsen don’t show up in wine tourism guides. They show up on growers’ maps.
The Contra Costa AVA was established April 15, 2024, as California’s 150th AVA, covering 167,146 acres in the East Bay. It took a long time to get official recognition, but the grapes have been good here for over a century.
The soil story — and why it matters
Most of what makes Contra Costa special starts underground.
The region’s vineyards are planted on an ancient alluvial sand bar at the confluence of the Sacramento and San Joaquin rivers. The Delhi sandy loam soil allowed these vines to survive the phylloxera epidemic that eviscerated most old vines in California, because the phylloxera root louse cannot survive in sand.
That’s not a small thing. Phylloxera — a root-eating louse — destroyed most of California’s old vineyards in the late 1800s and early 1900s. Growers everywhere had to pull up their vines and replant on resistant rootstock. In Contra Costa’s sandy ground, the louse couldn’t take hold, so the original vines just kept growing. Many vines date to the 1800s, dry-farmed with roots extending 40 or more feet deep.
What does 40-foot deep roots mean for the grape? It means the vine is finding its own water, far underground. The lack of water in the surface ground means vines produce small, concentrated berries with thick skins — which leads to concentrated wines with firm tannins and excellent structure.
We dry-farm our vines at Corteza — no irrigation. The vines do what vines in this soil have always done.
The climate — hot days, cool nights, and the delta wind
The soil is one half of the story. The climate is the other.
As California’s Central Valley heats up, a vacuum effect pulls cool air from the coast, and wind funnels through a gap in the Coastal Range. Even on hot days, the afternoons are windy, leading to a diurnal shift where nights and mornings stay cool.
Hot days ripen the fruit fully and build flavor. Cool nights slow things down and keep the acidity alive. That combination — warmth and freshness in the same growing season — is what winemakers are really buying when they source from Contra Costa. The tidal strait has also formed a vast sand-dune system, and the brackish water and wind support a distinct umami character in the wines.
Our vineyard in Knightsen sits with a view of Mount Diablo to the south. The delta wind hits us every afternoon. We farm naturally in this ground, and we have for ten years.
Who’s already buying Contra Costa grapes
We’re not the only ones talking about this region. Ridge Vineyards sources Carignane from Contra Costa. Sandlands — one of the most talked-about producers of Rhône and heritage California varieties — makes their Carignane from right here in Contra Costa County. Broc Cellars in Berkeley is one of our own grape buyers.
When producers like these seek out a region, it’s worth paying attention to why.
What we have for sale from this ground
We grow three varieties on our Knightsen vineyard, all available for the 2026 harvest:
- Grenache Noir — about 15 tons expected. Our 2023 vintage won Double Gold at the 2026 SF Chronicle Wine Competition — one of the highest honors at the competition, awarded only when every judge votes gold unanimously.
- Grenache Blanc — about 10 tons expected. A rare white in California, with real body and bright freshness.
- Carignane — about 5 tons expected. Deep color, natural acidity, firm structure — the grape Contra Costa has always been known for.
Quantities are limited. For current Brix, pH, and pricing, email cortezavineyards@gmail.com and we’ll send the latest numbers.
Reserve the fruit for 2026
Summer is when buyers lock in their fruit, before it’s spoken for.
- Wineries and cellars: Grapes for Wineries & Cellars
- Home winemakers near Brentwood, Oakley, Livermore, and the East Bay: Home Winemakers: Grapes Available – Reserve Yours Now
Or email cortezavineyards@gmail.com with what you need.
Rather drink it than make it?
If you want to taste what this soil and climate can do in a glass, you don’t have to wait for harvest. Our award-winning 2023 Grenache Noir is in our online shop right now — grown on these same vines, in this same ground, by the five of us who farm here.
FAQ
Where exactly is Corteza Vineyards? Knightsen, in eastern Contra Costa County — close to Brentwood and Oakley, and an easy drive from Livermore, Antioch, and most of the East Bay.
Is Contra Costa an official wine region? Yes. The Contra Costa AVA was officially established on April 15, 2024 — California’s 150th recognized American Viticultural Area.
What makes the sandy soil special? It drains fast, forces vines to grow deep roots, and — notably — kept vines alive through the phylloxera epidemic that wiped out most California vineyards. Many vines in this region survived ungrafted from the 1800s.
Do you ship wine? Visit our online shop for current availability and shipping details.
How do I reserve grapes for the 2026 harvest? Email cortezavineyards@gmail.com with your variety and amount. We’ll send current specs and confirm your reservation.
Reserve your 2026 fruit: wineries & cellars · home winemakers · cortezavineyards@gmail.com
Or just drink it: [shop the 2023 Grenache Noir]
