The residents of Starboard Court, Marin County, have been living the mid-century modernist dream since the actual mid-century. Of 10 original owners, five still live there, and no houses changed hands until 1991. Most of the residents are in their 80s and 90s, though their sprightliness suggests there’s a fountain of youth nearby. What’s more, they’ve barely changed their homes since they were built in the mid-60s. They simply haven’t needed to: it all worked fine and still does. If evidence was ever needed of what postwar American design got right, it’s all here, in an idyllic cul-de-sac outside San Francisco. As one resident puts it, “Nobody ever thought of leaving here unless they were carried out.”

It’s not hard to see what kept them here. Downtown San Francisco is a 15-minute drive away, over the Golden Gate Bridge, but Marin County feels like a different country. It’s a landscape of rolling hills, wooded valleys and rugged coasts, and unsurprisingly has become the habitat of weekend cyclists and celebrities (George Lucas’s Skywalker Ranch is just up the freeway). But, despite appearances, the 10 houses of Starboard Court are not bespoke luxury residences; they are mass-produced tract housing, albeit of the highest standard.

‘It’s amazing that we’ve been having dinners together for 45 years now,’ Betty Toole says of her neighbours. Photograph: David Fenton

They were built by a property developer named Joseph Eichler, a familiar name in northern California but virtually unheard of elsewhere. Between 1950 and 1974, he sold more than 11,000 homes across California. He knew next to nothing about architecture to start with – his family was in dairy farming – but Eichler made it his mission to bring the modernist dream within reach of ordinary Americans. Partly inspired by a Frank Lloyd Wright house he’d rented, he commissioned a team of San Francisco architects to come up with affordable designs that would be light and open, in terms of both their general ambience and their construction. True to modernist tenets, Eichler’s homes offered open-plan living areas, clean, geometric lines, exposed timber post-and-beam structural frames, and a continuum between indoor and outdoor space via skylights, floor-to-ceiling glass and, in the latter years, internal atriums, which became an Eichler trademark.

The houses in Starboard Court are all slightly different, as they were in most Eichler neighbourhoods. Steve Jobs claimed to have grown up in an Eichler near Palo Alto – his biographer Walter Isaacson recalls walking around Jobs’ childhood neighbourhood with him, where the Apple co-founder told him his childhood home “instilled his passion for making sharply designed products for the mass market”. The rest is history, except Jobs’ home wasn’t a genuine Eichler but an imitation, built by one of his rivals (Eichler owners call these “likelers”). Funnily enough, Jobs’ Apple co-founder, Steve Wozniak, did grow up in a genuine Eichler.

At the heart of Ave Couris’ home is a vast glass atrium. A section of the roof opens up to the elements. Photograph: David Fenton

“Eichlers weren’t counted as upscale houses at the time,” says Ave Couris, an estate agent who has lived in Starboard Court since 1974. “They had no status for years. It’s only recently, now that everybody’s into this ‘mid-century modernism’, that Eichler has really earned his due.”

Couris’s house is a typical late-Eichler design. A porch is created by the overhang of a giant pitched roof, a section of which slides back to open it to the elements. Through the front door, you’re greeted with a surprise: you’re not actually indoors, but in an atrium at the heart of the house. Bedrooms run along right, with an open-plan living and kitchen area straight ahead, beneath a cathedral-like roof that terminates with a brick chimney breast. To the rear, windows frame enviable views across the bay to the San Francisco skyline.

Ave Couris fell in love with her Eichler home at first sight, in 1974. Photograph: David Fenton

Couris and her ex-husband had never heard of Eichler, but the moment they walked in they sold their life insurance to put down a deposit. There was an open house the weekend before the sale was agreed. “People were walking around saying, ‘Oh my goodness, look how poor the quality is!’ We were thinking, ‘Thank goodness! Let’s hope they don’t buy it.’ Fortunately everyone disliked it apart from us.”

Early Eichler homes did have a reputation for flimsiness, but Couris has done practically nothing to hers in 40 years, beyond changing a few fittings and putting in tiled floors (the wooden ones didn’t wear well under her numerous pets). It looks enviably retro now. “If you live in a house long enough, the styles come back to the original,” Couris says over a cup of tea in the garden, hummingbirds flitting around us. “Now everybody’s putting Formica back in.” The tea is PG Tips; she originally hails from Nuneaton, and came to the US in 1958 as a nurse before retraining as an estate agent 30 years ago. Couris is in her 80s now, but still working.

It’s a similar story with Couris’s next-door neighbour, Phillip Perloff, a retired doctor. Perloff has barely done a thing to his house since he moved in. He wasn’t chasing the modernist dream, he says; he simply wanted a bigger house. “Being in an Eichler had a modicum of stigma to it: it was tract-house living.”

Phillip Perloff swims naked in his pool every morning. Photograph: David Fenton

Perloff, his wife and their two children moved in soon after the houses were built in 1965. “We warmed to it very quickly. It was so spacious, but it had a kind of coherence to it. It all fit together: a perfect family home.”

San Francisco was “magnificent” in the 50s, says Perloff, who is “93 and a half”, though he looks a good 20 years younger. He swims naked in his pool every morning. “It had everything young people could want: bohemians, a great artists’ colony, poetry, Allen Ginsberg, Mort Sahl, beautiful unbuilt vistas.” Perloff’s house still feels partly from that era. His atrium is a miniature jungle, the house is filled with craftworks, and the walls are lined with paintings he and his wife have collected over the years.

Betty Toole lives across the street from Couris and Perloff. When we meet, she’s wearing a vibrant Roberto Cavalli dress and a miniature kaleidoscope around her neck. Her house is strewn with them, it turns out, amid classic furniture from the same era as the house. “It’s amazing that we’ve been having dinners together for 45 years now,” she says of her neighbours. “Our kids used to play in the street together, then they were going to university together, now they’re grown up and are trying to get us to move out of these houses so they can have them.”

Toole’s Eichler is a rare exception in that it has two storeys. That creates space for a dramatic, double-height living room overlooked by a balcony bedroom. “It did lack intimacy,” Toole says. Unlike her friends and neighbours, she has made a few changes over the years. The kitchen has been painted to match her Saarinen Tulip dining chairs; she’s added a sauna and an office in the garage, a deck out the back and a Japanese garden out the front.

Phillip Perloff bought his Eichler home in 1965 and has barely changed a thing. Photograph: David Fenton

If anything, Toole’s house has an excess of light. She’s regularly had to change floor surfaces and fading textiles; the sun even cracked the glass of her Eames table. But the height also gives her more wall space to hang her art collection.

The houses at Starboard Court were some of the last Eichlers built, and were larger and more expensive than previous ones. At the time these neighbours moved in, the rest of their peninsula was vacant lots, owned by Eichler. But he overstretched himself developing high-rise properties in San Francisco and went bankrupt in 1967. He died in 1974.

In 1965, one of these homes would have cost about $64,000 (£42,000); today they’re worth closer to $3m. This is undeniably a bastion of privilege, but it’s notable that none of these veteran residents was born into wealth. For these people, at least, the American dream became a reality.