Donlyn Lyndon was a year or two out of architecture school when he and a few of his Princeton classmates set up what they called a “weekend practice” in Berkeley, Calif. They all had day jobs; Mr. Lyndon’s was teaching architecture.

It was the early 1960s, and the members of the group were, as the critic Robert Campbell put it, dropouts from Modernism, the orthodoxy of the moment. They shared a belief in a more humane and flexible architecture, one that allowed for the sensibilities of the people who would inhabit their buildings and that acknowledged the particular landscapes those buildings would inhabit.

They had been in business for only about an hour, Mr. Lyndon later joked, when they were invited to collaborate on an unusual project.

An architect turned developer named Al Boeke had envisioned a new kind of community on 5,200 acres of a former sheep ranch overlooking the Pacific Ocean, a few hours north of San Francisco — with buildings shaped by, and in deference to, the wild, windswept landscape.

Mr. Boeke hired Lawrence Halprin, the landscape architect who would later be celebrated for his work on Ghirardelli Square in San Francisco and many other urban plazas and parks; Joseph Esherick, an established Bay Area architect; and, at Mr. Halprin’s suggestion, Mr. Lyndon and his “weekend practice” partners, Charles Moore, William Turnbull Jr. and Richard Whitaker, who used their initials to name their new firm, MLTW.

The architects’ job was to design prototypes for buildings that others could follow — but they were suggestions, not prescriptions, Mr. Lyndon often said. The site was breathtaking, a sweep of meadowland that extended to the bluffs along a 10-mile stretch of coastline divided by hedgerows of half-century-old cypress trees.

It was Mr. Halprin’s radical idea to nestle some of the structures against the hedgerows and leave the meadows — in developer’s terms, the prime real estate — untouched. Mr. Esherick’s firm sketched out a clutch of diminutive, low-slung houses clad in redwood shingles with shed roofs tucked into a line of cypress.

MLTW’s assignment was to create something bolder, to show how larger structures could adapt to more exposed land; their site was a promontory with no shelter from the elements.

They designed a condominium building of 10 connected dwellings. Although it was a second-home community, their intention was to craft a kind of village, with common areas like the open meadows and other spaces that encouraged connections among neighbors.

The Sea Ranch, as the larger development would be called, was conceived, Mr. Lyndon wrote, as “a limited partnership — not a marriage — between the buildings and the land.”

He died on April 5 at his home there, his daughter Laura Lyndon said, almost two months after the death of his wife of 63 years, the artist Alice Wingwall. He was 90.

What he and his colleagues created was a stunning departure for its time: a collection of small, loft-like “houses” made from rough-hewn redwood planks, with enormous windows that framed the views, unified by a sloping shed roof to deflect the wind. It paid homage to the barns of the area with its post-and-beam construction and unpainted vertical cladding.

Though it had the unlovely name of Condominium One — they imagined other such structures would follow; they did not — what they built became an “icon of American architecture,” as the critic Paul Goldberger wrote in The New York Times in 1997, when Mr. Turnbull died. (It was placed on the National Register of Historic Places in 2005.)

Condominium One had the effect of raising a finger to the glass-and-steel boxes of the Modernist canon. It became a destination for generations of architectural pilgrims, with its funky, relaxed aesthetic serving as an inspiration for a new California style that would be replicated in ski and beach houses across the country.

Herbert Muschamp, writing in The Times in 1993, when Mr. Moore died, said that the group had elevated “the form of the simple shed to architectural grandeur.”

Mr. Esherick died in 1998; Mr. Halprin, in 2009; Mr. Boeke, in 2011; and Mr. Whitaker, in 2021.

Mr. Lyndon, who became a prominent academic and author, leading the architecture departments at the University of Oregon, M.I.T. and the University of California, Berkeley, was the last living member of the Sea Ranch gang, a bearded elder and longtime steward of the ethos and ideals they set forth.

“They were more like a band than an office,” Kevin Keim, the director of the Charles Moore Foundation in Austin, said of the members of MLTW in an interview. “They complemented each other in all kinds of ways. They often said their design mode was to sit at a round table with only one pencil between them, and if your idea faltered, you handed it to the next guy.” (The story, he allowed, may have been apocryphal.)

Mary Griffin, an architect who studied with Mr. Lyndon at M.I.T. and went on to marry and work with Mr. Turnbull, said: “Donlyn was the intellectual. He built with words.”

Like many great bands, they soon broke up — in their case, after their initial work at the Sea Ranch was completed, in 1965. Not because of any discord, but because other opportunities beckoned. Mr. Lyndon headed to Oregon, and then Cambridge, Mass., finally returning to Berkeley in 1978.

With his former colleague Mr. Moore and another co-author, Gerald Allen, he wrote “The Place of Houses” (1974), a gentle anti-manifesto that did not prescribe one style over another. It was a plain-spoken, poetic guide to how to think about making a home — the order of rooms, the placement of windows — using examples from a Japanese teahouse, Palladian villas and, yes, the Sea Ranch, places that were touchstones for the authors and examples of shapes and spaces that made people feel good. (Mr. Lyndon loved a bay window, and nooks to curl up in.)

Some critics saw the book as a paean to nostalgia, but others praised its humanism and lack of pretense. Jane Holtz Kay of The Nation called it “a consciousness raiser for houses.” Mr. Campbell of The Boston Globe described it as “a cleareyed blast at conventional wisdom of every sort on the subject of houses.”

As Mr. Lyndon and his co-authors wrote: “Anyone who cares enough can create a house of great worth — no anointment is required. If you care enough you just do it. You bind the goods and trappings of your life together with your dreams to make a place that is uniquely your own. In doing so, you build a semblance of the world you know, adding it to the community that surrounds you.”

Donlyn Lyndon was born on Jan. 7, 1936, in Detroit. His mother, Dorothea (Zentgrebe) Lyndon, was an educator. His father, Maynard Lyndon, was an architect who chose his eldest son’s first name for its euphony with their surname, creating what Donlyn — who never answered to Don — approvingly called “a syllabic palindrome.”

Donlyn won a scholarship to Princeton, where he studied architecture, earning his bachelor’s degree in 1957 and his master’s in 1959. He met Alice Atkinson, an artist, at Berkeley; they married in 1963.

When she began to go blind in her 30s because of a condition called retinitis pigmentosa, she turned from sculpture to photography. In 1980, she changed her surname to Wingwall, inspired by the broken wing of a stone angel on a building in Rome. “I have a broken wing, too,” she said. (Mr. Lyndon embraced it: “What does Wingwall think?” was a common refrain in their household.)

The house Mr. Lyndon built for them at the Sea Ranch was decorated in her favorite colors: orange, yellow and red, the last color she was able to see.

In addition to their daughter Laura, Mr. Lyndon is survived by another daughter, Audrey Lyndon; a son, Andrew; five grandchildren; a brother, Maynard; and a sister, Jo Lyndon.

Mr. Lyndon was the author, with Mr. Moore, of “Chambers for a Memory Palace” (1994), an architectural world tour and epistolary dialogue between two lions of architecture about the design of places they loved. Mr. Lyndon’s history of the place he loved most, “The Sea Ranch: Fifty Years of Architecture, Landscape, Place and Community on the Northern California Coast,” with photos by Jim Alinder, was published in 2004 and revised in 2013.

There are now more than 1,800 houses at the Sea Ranch, at least 10 of which Mr. Lyndon had a hand in designing, though it did not exactly evolve into the environmental utopia its creators envisioned.

A design committee still reviews all new construction and landscaping, but as development has intensified, the houses have grown larger. Climate change has brought additional challenges: finding building materials that are fire-safe, and firescaping the land, particularly the hedgerows, which are dying off.

“Place, and its nurture,” Mr. Lyndon and Mr. Allen wrote in the revised edition of “The Place of Houses,” published in 2000, “remains an essential breeding ground for civic virtue. The sustenance of our democratic republic, we believe, demands it.”