About halfway down the highway that dips and turns through the dairy land between Petaluma and Bodega Bay, a sign reads, “Welcome to Two Rock Valley. We’re Proud of It!” Your eyes scan the green hills for the promised two rocks, but all you see are scattered mounds of gravelly basalt. Suddenly, there they are: two moss-speckled boulders, sitting side by side like San Francisco’s Twin Peaks.

Once a trail landmark for American Indians, Two Rock sits in the middle of Marin-Sonoma’s historic dairy country. The area may not look all that different than it did a half-century ago, with low-slung milk barns and Victorian farm houses set among the tiny villages of Bloomfield, Tomales and Valley Ford. But take a closer look and you’ll see a younger generation of dairy farmers shaking off their traditional roles.

Rather than sell off all their milk to large milk companies or cheese makers, as they’ve done in the past, fifth- and sixth-generation ranchers, along with a handful of newcomers, are making their own brands of cheese, ice cream, yogurt and butter. These new businesses — actually a return to the pre-20th century dairy farm model — can be the key to saving the family farm.

“We have the desired milk for cheese and butter and yogurt. Why not make our own?” says fourth-generation rancher Karen Bianchi-Moreda of Valley Ford Cheese Co.

Though she still sells milk to Petaluma cheese company Bellwether Farms, Bianchi-Moreda began making cheese from the milk of her 500 Jersey cows in 2008 in a small dairy inside the farm’s 150-year-old milking barn. Now her sons Joe, 27, and Jim, 25, are slowly taking over cheese production and animal husbandry respectively after studying those subjects at Cal Poly San Luis Obispo.

“If it was just a fluid dairy (that sold only milk) it probably would have not been possible for her sons to return to the dairy,” says Steven Knudsen of the Sonoma County Farm Bureau, referring to Bianchi-Moreda. “Because of that, they can continue the farming tradition that has been in her family for numerous generations.”

Farmstead creameries like Valley Ford are a different breed than companies like Cowgirl Creamery, which purchase milk from dairy farmers. Dairy farmers who also make their own branded cheese or yogurt — called value-added products in ag school — get a better margin for their milk. In recent years, as feed prices have gone up exponentially and animals have needed more supplemental food since the drought has resulted in less green grass for grazing, value-added products provide a better chance to earn a profit.

“The goat milk price barely covers the cost of what it is to run the dairy,” says Anna Hancock of White Whale Farm and Pugs Leap Cheese. “We knew that with making cheese the margin was so much higher.”

Petaluma has been the center of Bay Area dairy production since the Gold Rush. It’s now the headquarters of larger regional companies like Clover Stornetta Farms and Straus Family Creamery, which became the country’s first certified organic creamery 20 years ago. Many traditional cow milk producers in the area have since converted to organic to get higher prices, especially since they’re competing with large-scale producers in the Central Valley, who maintain much less land per animal.

Artisan cheese making in Sonoma and Marin, which adds up to $120 million in annual sales, according to UC Cooperative Extension, goes back to the founding of Marin French Cheese 150 years ago. When Laura Chenel launched her goat cheese company in 1979, she helped usher in a new era of regional cheese making. The latest entries to the dairy world work with a mixture of dairy animals and breeds, from East Friesian sheep to Italian water buffalo.

“There’s been a second wave of cheese and dairy culture in the Northern California area,” says Louella Hill, president of the California Artisan Cheese Guild, cheese-making teacher and author of “Kitchen Creamery,” which will be released by Chronicle Books next week (see Page 3). “There was this amazing momentum that happened in the ’70s and ’80s that got the cheese culture established. Those companies have transformed — they’re different and bigger. Now there’s this next generation.”

Marissa Thornton, 27, is part of that next generation. She’s slowly converting her family’s 160-year-old ranch to a farmstead creamery that will produce yogurt and butter labeled Marshall Home Ranch and Dairy.

Thornton’s ancestors founded the Tomales Bay town of Marshall and once owned 20,000 acres in the area. Her father almost lost the original 1,000-acre family ranch when he inherited it in 2000 because of estate taxes that added up to over half the land’s value. He was forced to sell off his dairy cows but avoided having to sell the land when the Marin Agricultural Land Trust provided an agricultural easement.

After a Kickstarter campaign that raised almost $50,000 last year, Thornton was able to reestablish the dairy and now milks about 75 sheep and 12 Jersey cows almost solo. She sells the milk to Bleating Heart Cheese, which has a creamery on the ranch, but when that cheese maker outgrows the space, Thornton’s plan is to make yogurt and butter there.

“I’m very proud of our ranch,” she says. “I feel very honored to have my ancestors coming from here, to be a sixth generation. I just want to brand that and to put my name on something.”

Despite her family’s troubles holding onto their land, Thornton still has an advantage over beginning farmers without property. Joe and Missy Adiego of Haverton Hill Creamery couldn’t afford to buy land when they started their sheep dairy in 2010, and they now lease three plots around Tomales. They built a mobile creamery in case they ever have to change locations.

Missy, 32, says theirs is the first sheep dairy in the United States to sell its own brand of bottled milk. They also sell sheep’s milk ice cream and butter.

“We felt like because we’re young we have to do something different,” says Missy. “That’s part of being younger and farming. We’ve got to keep it moving.”

Joe’s grandfather was a cattle rancher, and his father sells dairy equipment. But when Joe, 30, decided to sell sheep milk, everyone, including Missy, thought he was crazy. Because sheep produce so little milk — about half as much as goats — the milk retails for $10 a quart. But the milk has at least twice the protein as cow’s milk, and those who are lactose intolerant can usually drink it. After Whole Foods expressed interest, the Adiegos began bottling; the milk is now sold at dozens of Bay Area markets.

San Francisco native Anna Hancock, 32, and her now ex-husband, Daniel Conner, also took risks when they launched White Whale Farm goat dairy in 2008. She was a law student who had gotten hooked on the country life during farm camp. When Pugs Leap Cheese went up for sale, they bought it somewhat on the spur of the moment even though the creamery was located in Healdsburg, an hour’s drive away.

Hancock spent a year hauling milk cans in her Subaru to Healdsburg every other day. She took a break to take the bar exam — she passed — and then built a creamery inside the farm’s century-old barn in 2013.

“My ex realized he’s not a farmer, but I am,” Hancock says. The two split amicably. “You have to love the whole lifestyle.”

Sharing the farm with her enormous Anatolian shepherd, Samson, and her curly-haired Mangalitsa pig, Bubbles, Hancock employs a cheese maker and herd manager. Gypsy Cheese Co. also has been renting Hancock’s creamery and using her milk in its cheese, but Hancock’s goal is to use up the milk from her farm’s 120 goats in Pugs Leap cheeses by May.

No one in the local dairy industry is forging an easy path. Joe and Missy Adiego work nonstop, even with help from Joe’s parents, both in the business and in taking care of the Adiegos’ young daughters.

“I often joke I have tears in my ice cream,” says Missy. “It’s a wonderful lifestyle but it’s a hard lifestyle, especially with a family of four and 1,200 sheep. But we were really adamant about it being a farmstead operation. It’s super important to be hands on.”

Tara Duggan is a San Francisco Chronicle staff writer. E-mail: tduggan@sfchronicle.com Twitter: @taraduggan