Joel Peterson founded Ravenswood winery in 1976. (Ravenswood)

In the fall of 1976, a San Francisco medical laboratory scientist named Joel Peterson bought seven tons of zinfandel grapes. He made wine by hand, in open-top fermentation tanks, punching down the grapes with a makeshift tool he fashioned himself, using techniques he had learned while apprenticing with Joseph Swan, a noted Sonoma County, Calif., winemaker. He ended up with 327 cases of wine.

That was the first vintage for Ravenswood, which would become one of California’s most influential wineries and a major champion of the Golden State’s signature grape. Peterson was bucking a consumer tide: Zinfandel was best known as “white zinfandel,” in fact a slightly sweet, mostly insipid pink wine that appealed to the sweet tooth of American soda drinkers (and gave rosé a bad reputation it has only recently overcome). Peterson and his business partner, W. Reed Foster, coined the slogan “No Wimpy Wines!” to counter the white zinfandel image and promote his wines as robust expressions of California’s climate and terroir.

This is a banner year for California wine anniversaries. The Robert Mondavi Winery turned 50 in July, and in May the winners of the 1976 Judgment of Paris wine tasting celebrated four decades of the marketing event that keeps on giving. Amid that hoopla, Peterson has been relatively low-key in marking his own milestone. But he took a break last week from shoveling grape skins and stems from fermentation tanks at Ravenswood’s winery near the city of Sonoma to reminisce in a phone interview.

“The wine business has changed substantially since I started,” Peterson said. “It was smaller and simpler back then. We sold all the wine ourselves.”

Small wineries could not rely on distributors to build their markets, so Peterson hit the road to tell his own story. Luckily, he was good at it. His first target market was Washington, D.C., and he found a receptive retailer in MacArthur Beverages. Gradually, he established a foothold in other markets.

“The sophistication of the wine-drinking public has really changed, and it’s a wide-ranging group,” Peterson says. “Back then, there were small pockets of people in food and dining clubs. They were mostly beer drinkers, but they were receptive.” He still travels about a third of each year to visit markets and meet consumers at winemaker dinners and other events.

Ravenswood never owned vineyards. Peterson cultivated relationships with family growers who tended older vineyards of zinfandel, those gnarly, thick-trunk vines still scattered throughout California. Vineyard names such as Pickberry, Dickerson, Teldeschi, Belloni and Old Hill are familiar to Ravenswood fans. He also crafted county-designate blends, which were more affordable. One of my favorite wines early in my grape explorations was Ravenswood’s Sonoma County Old Vine Zinfandel. And today, one of the best ways to explore the effect of terroir on wines is to compare Ravenswood’s single-vineyard zins from the same vintage.

Other wineries followed a similar model — most notably Ridge and Rosenblum, who along with Ravenswood became known in the 1980s and 1990s as “the three Rs of zinfandel.” The model is followed today by Peterson’s son, Morgan Twain-Peterson, with his Bedrock Vineyards label, and a few other young vintners working to preserve and rehabilitate California’s oldest vineyards.

Peterson created the inexpensive Vintners Blend series of wines with a statewide California designation. They established Ravenswood as a national brand and satisfied distributors who wanted something cheap and easy to sell. Some wineries have struggled with the tension between cash flow and wine quality, but Peterson managed to build Ravenswood in size while maintaining focus on the single-vineyard zinfandels.

“Of course, the larger-volume wine becomes your center of gravity,” Peterson says. “But my focus remained the single-vineyard-designate wines and the county wines, because they reflect the character and sense of place of the vineyards.”

Ravenswood was acquired in 2001 by drinks conglomerate Constellation Brands, which turned the Vintners Blend line into a widely available supermarket brand. Peterson became senior vice president of the parent company, working on winemaking and marketing for all of Constellation’s wine brands. Now 69, he stepped back from that position recently, retaining the title of “Founder/Winemaker” at Ravenswood, working with director of winemaking Gary Sitton.

“What I like about this business is the winemaking, the viticulture and the interaction with people at all levels,” Peterson told me. “So I still go meet with the growers, check on the vineyards, taste the wines every day and participate in the blending. I don’t do purchase orders or HR, thank goodness.”

And he misses the old days of making wine by hand. “I’ve started another little project I call Once and Future Wines, making wines like I did with Joe Swan: small, open-top fermenters, punch down by hand, all small lots,” he says, the excitement evident in his voice. “So when I do retire from Ravenswood, I will not actually retire. I have my projects to keep me engaged.”

I asked what tool he would use to punch down the fermenting grapes, since his handmade one from the 1970s is now on display in the Smithsonian’s National Museum of American History.

“I made two!” he said. “I still have the other one.”