PORTOLA VALLEY -- If the architecture of Silicon Valley calls to mind the tilt-up office parks that surround its freeway exits, you might have missed Beverly Thorne’s jagged, steel-framed house nestled in a cliff overlooking the South Bay.

The airy home is one of the most stunning of an estimated 30,000 mid-20th century Modern houses dotting the region from San Jose to San Francisco that are attracting new admirers among monied young software engineers with an affinity for clean designs.

“They call us the underground ‘Midmod’ society,” said Monique Lombardelli, who helps discover the homes for the tech elite. “A lot of my clients are Facebook buyers, Google buyers. They love design. They’re into form and function and the simplicity of California living. They’re not into huge McMansions.”

Software designers who spend their days working on UX or UI — user experience or user interface — find a kindred aesthetic in the simple, brightly lit and flat-roofed Modernist homes built by real estate developers such as Joseph Eichler in the 1950s and 1960s, said Rob Castaneda, founder and CEO of Palo Alto-based startup ServiceRocket.

Describing the first time he entered an Eichler like “using a Nokia phone and then using an iPhone,” Castaneda said the simple design challenged him and took his breath away. His family now lives in one.

He got help finding the Eichler from 36-year-old Lombardelli, who rides around on weekends in a black Corvette with a license plate that says “MIDMOD.” She’s on a mission aimed at preserving the homes and “getting the right people to buy them so they’re not torn down. They’re really works of art.”

Rather than simply trying to capture the nostalgic glamor of the “Mad Men” era, Lombardelli, a broker and CEO of Modern Homes Realty, insists there’s a deeper ethos behind Silicon Valley’s Modernist love.

“We’re minimalists, joined by wanting to preserve these homes,” she said. “People either get it or they don’t, and those who don’t either tear them down or ruin them.”

Wearing YouTube sweatshirts and driving Teslas, the enthusiasts who took a self-guided home tour organized by Lombardelli on Saturday shared her vision. The tour followed a 30-mile ribbon of boxy gems along the San Francisco Peninsula, from suburban Sunnyvale to the famous chalet-style “Life House” in the San Mateo Highlands designed by architect Pietro Belluschi and built by Eichler’s firm in 1958. Stops included Palo Alto —the “mothership of Eichlers,” Lombardelli said — and a brand-new Belmont home built in the midcentury style.

There are not enough Eichlers, Doelgers and similarly-styled vintage homes for all the people who want them, Lombardelli said.

Although some now deride the midcentury trend and the furniture knockoffs it has spawned as out of fashion, enthusiasts say the ongoing obsession suits Silicon Valley’s open-source values.

Touring the homes looking for furniture ideas, Max Burton said the resurgence is based on Modernism’s “honest construction, honest materials, interesting ways of living.”

“People are more interested in Modernism when they feel optimistic about society and life,” said Burton, founder of San Francisco design firm Matter. “It’s not a style, it’s a philosophy, a way of looking at life.”

Ironically, many of the million-dollar houses now coveted by affluent buyers were originally built as low-cost tract homes with middle-class families in mind. But there were always high-end exceptions.

Few are as breathtaking as the structure architect Thorne built in 1960 for a Bethlehem Steel executive in Portola Valley. Thorne used tapered I-beams to hold up a roof that appears to float over the cliff where it is perched.

“You can see all of Silicon Valley, from Moffett (Field) to San Jose, and it all lights up at night,” said owner Mike Nuttall as he greeted guests in his living room. “We just love it every day.”

An Apple marketing director lived in the home before Nuttall, co-founder of product design giant IDEO, moved in 22 years ago. But it was Apple’s late leader, whose childhood home was a compact Eichler look-alike in Mountain View, whom Nuttall credits for the newfound dedication to the sleek and simple.

“There’s a resurgence of interest in design,” Nuttall said. “I actually thank Steve Jobs for that. Products are cool again, and architecture is sort of a product.”

“A lot of the new wealth these days is younger people, and they want something different from their parents’ traditional homes,” he added. “These homes are fresher, they’re more open, they express a more optimistic view.” Contact Matt O’Brien at 408-920-5011. Follow him at Twitter.com/mattoyeah .