In the 1920s, decades before the term “affordable housing” was coined, the prominent developer Alexander Bing joined forces with a few renowned urbanists and intellectuals to build a “garden community” of about 1,200 units on 77 acres in Queens left over from the construction of the Long Island Rail Road’s Sunnyside train yards. Called Sunnyside Gardens, it was one of the first home-ownership projects in the nation to target low- and middle-income families. Despite some hard times since the 1950s, in which demand for units was low and upkeep was neglected, Sunnyside Gardens is again flourishing, with young couples from Manhattan and Brooklyn moving in to join longtime residents that have held on to their property for years. And, amazingly, homes are still affordable by Manhattan standards, with recent sales in the low $400,000s.

The development’s little one-, two-, and three-family houses were designed by architects Clarence Stein and Henry Wright to be modest, but the ideas behind them were majestic, and are still embraced by at least some current residents. The governing principles were “health, open space, greenery, and idyllic community living for all,” with houses situated to maximize sunlight and breezes. Workers would live beside managers, chauffeurs and mechanics beside bosses, tradesmen across from professors. All ethnic groups were welcome to live in peace and harmony, sharing large common courtyards as well as a community garden. Architecture critic Lewis Mumford, who moved to Sunnyside from Brooklyn Heights in 1925, regarded it as a new paradigm for urban development: close but still separated from the city’s center; enclosed in greenery; and free of the automobile, which was only beginning to wreak its havoc at the time.

Designer Susan Shaw and her husband, architect Jack Freeman, moved to Sunnyside from Manhattan in 1988, fascinated by its idealistic heritage. “Sunnyside was always sort of leftish,” said Ms. Shaw. “It was designed by visionary architects and attracted creative people – artists, writers, teachers – who were community-oriented.” Indeed, in its early days, Sunnyside lured so many writers and artists expecting children that it was called “the maternity ward of Greenwich Village.”

“I really feel that this is a neighborhood, with true community spirit,” said Betsy Crawford Leavitt, who moved to Sunnyside from Manhattan. “I can go next door to borrow a cup of milk, or ask the neighbor across the street to take a UPS package when I’m away. We have a blend of people and ethnic groups. Some are struggling, but we make it work.”

The gardens and common areas elevate the appearance of what otherwise would be rather plain houses. The simplicity of the buildings and the tightness of the living quarters were core principles of the modernists, who also believed that beautiful public spaces would promote community. Staying within the city grid (the city government refused to grant an exemption), the architects laid out close groups of narrow houses and apartment buildings, many fronting on common greens that were intended for “restful gatherings or for quiet play.” To preserve the harmony of the greens, easements were placed on all the deeds, forbidding individual property owners from converting common land to private use. When the easements began expiring in the 1960s, some homeowners put in driveways, fences, and additions to their houses.

In response to political pressure from some residents, in 1974 the city declared the neighborhood a Special Planned Community Preservation District, which required the issuance of special permits for most property alterations. However, the permit requirement often went unenforced.

In 1984, Sunnyside Gardens was designated a national historic district. Now some residents are hoping to get a stricter city landmark designation that would prevent any further changes to facades or common areas.

Some residents said that houses on the common courts that have remained unchanged have higher real estate values than those that have been cut up or appropriated by owners for private use. “I think it depends,” says Robert MacKay, who bought a house six years ago on Hamilton Court, one of the most intact courts, for a price in the low $200s.

“I had my eyes set on Sunnyside for years when I lived nearby in Woodside. I loved the trees, the canopy, the common green spaces, and the stability of the spaces. But I understand that some people want the freedom to do whatever they want with their property.”

He guesses that his house, now almost fully renovated, would sell for close to $600,000.

The most recent sale in the area was an original house – with original plumbing and original electrical wiring at 50 amps – that was bought by a young couple for $410,000, said real estate broker Dorothy Morehead. A block away, a fully upgraded, renovated two-and-a-half-story house sold for $635,000. “The scale here is very human,” said Ms. Morehead, who believes so much in the neighborhood that she recently opened a restaurant, Bliss, on 46th Street and Skillman Avenue. “I was showing the property as a broker,” she said, “and I thought: How often does a corner property next door to what you already own come on the market? I bought it, and we’re doing very well, serving good, innovative American cuisine.” Her clientele is mainly from the neighborhood, with more and more customers coming from Manhattan and Brooklyn.

Despite the neighborhood’s warm, communal feel, managing common areas – even with a socialist heritage – is never easy. Children are not permitted to play in the common courts, which can be a shock to new homeowners.

“When we moved in,” said Ms. Shaw, “a neighbor came by to say “nice to know you, and by the way, children aren’t allowed in the courtyards.”

The lovely park three blocks away eased Ms. Shaw’s shock. “Now we have someone from the trustee association greet newcomers, giving them the documents and the easement agreement. We try to educate people as they move in.”

Even the park, though, has an arrangement unique to Sunnyside Gardens. It’s a 3-acre private park, said Mr. MacKay, but not elite. Anyone can join. The annual fee is $162, plus 12 hours of volunteer work. “Everyone knows one another. The kids have lots of friends. We have fields, basketball courts, sand boxes. We have two kids, and the park was a lifesaver.”

So is there any downside to all this communal goodwill? “Well,” said Ms. Shaw, “we sold our apartment in Manhattan for something like $350,000. It would sell for around a million today. Do the math.”