Joseph Eichler, creator of the popular Eichler homes that dot California (and a tiny bit of upstate New York), was neither an architect nor a designer. A developer with an interest in the work of Midcentury Modern icons such as Frank Lloyd Wright and Mies van der Rohe, Eichler built around 11,000 homes that became known as the California Modern style in San Francisco and parts of southern California between the late 1940s and early 1970s.

Eichler was particularly inspired by Wright’s Bazett House in Hillsborough, California, which he rented during World War II. The Usonian-style home, initially built for Sidney Bazett-Jones and his wife in the 1930s, was constructed in a double V-shape with red brick and redwood walls and a large central chimney. When Eichler rented the home, he allegedly grew so attached that he attempted to sabotage attempts to sell the property. (He was ultimately unsuccessful; it was sold to Betty and Louis Frank in 1945, and the Eichlers were evicted.)

After his time in Bazett House, Eichler moved on to design similar homes of his own. Built as much on post-World War II optimism as they were on Eichler’s personal design ideals, the homes featured many elements similar to those of Wright and van der Rohe. The low-slung homes focused on the organic, constructed with local materials like redwood and including large glass windows that blended the natural world with the built environment. Open-air atriums, a feature in many of Eichler’s homes, created a buffer between inside and outside and let in plenty of California sunshine.

Eichler also became an early adopter of the open floor plan to make public spaces, including the living room, kitchen, and dining room, more functional. He used sliding doors and Shoji screens in many of his original homes to make small spaces more efficient and add a touch of Asian-inspired flair popular at the time.

It’s clear that Eichler borrowed from the Midcentury greats when it came to his designs, but a key difference was the equal value he placed on clean design and affordability. While most Midcentury Modern homes were considered high-end during the 1940s and ‘50s, Eichler was determined to mass-produce homes accessible to the middle class. His first tract of 50 three-bedroom, one-bathroom homes sold for $10,000 each. According to Curbed, homes ranged from $34,950 to $46,500 in 1962, which translates to between $284,800 and $379,00 today.

The people who bought Eichler Homes during the 20th century were similarly interested in both egalitarianism and beautiful design. According to NPR, early buyers included artists, a Disney animator, and elementary school teachers in San Francisco, as well as emigrants from Midwest states looking for jobs in aerospace, oil, and entertainment in southern California. And Eichler didn’t just make his homes affordable—he also encouraged racial integration in his neighborhoods.

Throughout his lifetime, Eichler received acclaim for his architectural and economic innovations and his influence on the way we think about modern design. Unsurprisingly, Eichler homes remain popular today—most sell for around $1 million. According to Eichler real estate specialist Renee Adelmann, the homes continue to attract a variety of owners, from architecture and Midcentury Modern nerds to baby boomers looking for a lower maintenance place to live out their retirement.

Current homeowners enjoy the timelessness of Eichler homes, which can be updated to include more modern amenities. Still, Adelmann says, there’s something special about coming across an original Eichler.

“That’s my favorite, what I call a grandma and grandpa,” she explains. “It’s in pristine condition, and I keep it in its original state. But it’s really important to me as a realtor and someone who loves Eichlers to make them livable. [I think] he would be okay with the updates!”

It’s a good thing the homes are so amenable to changes, because Eichler homes (like any historic building) run into their fair share of maintenance issues. Since most roofs on Eichler homes are flat, water pooling can lead to damages that end up in a roof replacement every 15 to 20 years. And the homes’ expansive windows, though they let in a lot of light, are single-pane and not tempered or as energy-efficient as 21st-century windows.

Plus, about half of the homes built between 1955 and 1957 were constructed with now-defunct radiated heating systems. One solution in these instances has been The Unico System (a 16-year partner and sponsor of the National Trust). Because the small-duct central air system is designed to be unobtrusive, Adelmann says it’s “a really nice solution that doesn’t take away from the integrity of the house.” As such, the heating and cooling system has already been installed in over 600,000 homes in the United States, including many Eichler homes throughout California.

Despite these maintenance challenges, few homeowners regret purchasing an Eichler home. Just as they did decades ago, these places tend to inspire a more modern way of living.

“I’ve owned and lived in two atrium model Eichlers within the past 14 years,” Adelmann says, “and I love these homes and their simplicity. But the thing that people really like about the homes is … this idealistic idea of California modern design.”