The unassuming white farmhouse in the far reaches of Western Sonoma County wears a modest face from the road. But it hides a high-falutin' secret.

The two-story house, built in the 1970s by Charles and Sophia Hunt on their 160-acre Two Rock ranch on what is now Joy Road, has a Hollywood resume.

It housed an unruly brood of children in the opening scenes of the 2003 Steve Martin comedy, "Cheaper by the Dozen." The bucolic setting, with its 19th century redwood barn, small apple orchard and rustic little milking cabin where their 21-year-old daughter Lydia now lives, have been used as backdrops in commercials for everything from Chick-fil-A to Subway Sandwiches and in catalogs like L.L. Bean and Sundance.

It is now one of the featured attractions on the upcoming Heritage Homes of Petaluma Biennial Summer Home Tour on Sept. 16. It's a dramatic departure from the usual bungalows and Victorians on Petaluma's photogenic old west side that are usually showcased on the tour. But it will also provide a rare look at a farmhouse that was typical of the rural dwellings dotting the rolling countryside between Petaluma and the coast.

For Joe and Kathy Tresch, this sweet spot sought out by so many location scouts is simply Olympia's Valley, named for Joe's grandmother Olympia Nonella, who was raised and died on a neighboring ranch her Swiss immigrant parents settled on the other side of Walker Road in 1905.

Except for two years spent at Chico State University finishing up his degree in dairy husbandry, Joe has also spent his whole life in this valley working that same family land, known as the Deer Valley East and Deer Valley West dairies.

"My vocation is my avocation. I pretty much like what I do and I like to be left alone to do my own thing and it seems to work," says Joe, a laconic man who during the early years of his marriage didn't own a registered car and left the ranch only once a year to go visit the accountant.

Over the years the Tresches have scraped together the funds to buy up neighboring ranches, including the old Hunt ranch, eventually amassing more than 2,000 acres on which they graze some 750 Holstein and Jersey cows. They've sold their certified organic milk to Straus Family Creamery for 17 years. In January they bought 160 acres of the former St. Anthony's rehab farm.

The Treshes survive in Two Rock — where the number of dairies has dwindled by more than half just in Joe's lifetime — by adapting, seizing opportunities like the shift to organic, and diversifying.

Kathy tends Olympia's Orchard, a fertile fruitbowl featuring 50 different varieties of apples. She actually has two orchards: One small stand in back of the old Hunt farmhouse and another two acres deep on the ranch bordered by hedgerows of natives and hidden beneath the flank of a hillside crested with oak, bay and fir.

During the fall apple harvest she hand picks eight bushels a day that she sells at the Occidental and Sebastopol farmer's markets and at her own honor stand at the Olympia's Valley gate. But the family's latest venture is at the Hunt Farm, rechristened Olympia's Valley and turned into a Martha Stewart-like wedding venue. The Tresches bought the property about seven years ago from Kathy's cousin, who had owned it for some 25 years and had done most of the major restoration and renovation.

This is the part of the property that visitors will see on the Heritage Homes tour. They can walk the lower floor of the photogenic old farmhouse, with its long front porch and steeply pitched gables. They can also mosey over to the rustic 19th-century barn where, during weddings, guests stroll the haylofts and dine and dance in agrarian style beneath crystal chandeliers.

"What we're trying to present now is a kind of a simpler time, more connected to agriculture. We don't want to be overly pretentious," Kathy says.

All three kids, 25-year-old Lindsay and 21-year-old twins Lydia and Joe, work on the ranch, and all are committed to working it beside their parents.

Visitors to the ranch will see a simply decorated farmhouse with a landscape left largely to Mother Nature.

"We're showing that the apples pay for what happens here," she said. "What's generated on the ranch is invested on the ranch."

You can reach Staff Writer Meg McConahey at meg.mcconahey@ pressdemocrat.com.