Many 20th-century architects, it seems, are mama’s boys. Le Corbusier carried on a famous correspondence with his mother until her death in 1960, assiduously detailing his every accomplishment in letters to her that span the entirety of his adult life. Frank Lloyd Wright, too, adored his mother, extolling her virtues in particular length in his memoirs. Like Corbusier, Robert Venturi built a house for his mother. In doing so, he spearheaded a movement in postwar design that brazenly defied Corbusier’s rational modernism. The Vanna Venturi House — the structure that opened the floodgates of Postmodernism — proved nothing short of revolutionary when it was completed in 1964. With the release two years later of Venturi’s canonical text “Complexity and Contradiction in Architecture,” the building he continues to call simply “mother’s house” became a paragon of architecture’s mannerist turn. Last week the residence, located in Philadelphia’s Chestnut Hill neighborhood, again caused an uproar when it appeared on the market for the first time in 43 years. The asking price, $1.75 million, though high by Philadelphia standards, is reasonable when compared with valuations for properties of similar historic significance elsewhere.

It’s not very often that a building featured in nearly every textbook on 20th-century architecture is also featured on myriad real estate sales websites. The house is a primer in Postmodern design history. “To the amateur eye it can be puzzling,” states Realtor.com, “but with some education about its juxtaposition of traditional design against more complex forms, its status as a groundbreaking residential design becomes clear.” Broker Melanie Stecura, who is handling the sale, emphasized that “it’s certainly a livable house,” albeit one that may not afford much privacy: “If you can imagine living there, people come and knock on your door all the time.”

Still, even if a new owner were willing to open up to the occasional unannounced visitor, the question remains: Given the sheer architectural significance of the Vanna Venturi House — and the collective benefit to be gained from its availability to students, scholars, and design fans — shouldn’t it be preserved and accessible to the public forevermore?

On one hand, the house doesn’t face any of the usual preservation-related threats. It is structurally sound and was diligently maintained by its longtime owner, Thomas P. Hughes, a former University of Pennsylvania professor who passed away last year, with Venturi himself supervising any renovations. Moreover, the Hughes family, which is selling the building, is only considering potential buyers who intend to be stewards as diligent and conscientious as their late father.

On the other hand, this sale presents a golden opportunity for the National Trust for Historic Preservation to step in. The organization has in the past acquired buildings of outsize historical significance that were not in danger of falling into disrepair but whose potential transferal from one private owner to another could prevent the public out from visiting and benefiting from its significance. That is, the National Trust has intervened in select cases when the issue was one of ensuring access.

Take Mies Van Der Rohe’s 1951 Farnsworth House, in Plano, Illinois. The definitive exemplar of a Modernist residence in North America was put up for sale in a Sotheby’s auction of important 20th-century design in late 2003. Preservationists worried that a developer had plans to bid on it and possibly relocate it to another site. The National Trust and Preservation Illinois raised $7.5 million to buy the property, each contributing $1 million to a fund that was supplemented with more than 350 contributions from private individuals that ranged from several dollars to $250,000. The Farnsworth House is but one of several highly important mid-century homes owned, operated, and opened to the public by the trust. Other examples include Frank Lloyd Wright’s Fallingwater, in Bear Run, Pennsylvania; Walter Gropius and Marcel Breuer’s Gropius House, in Lincoln, Massachusetts; and Philip Johnson’s Glass House, in New Canaan, Connecticut. The Vanna Venturi House is of no less historical significance.

If the National Trust were to acquire the building, the organization would be making a claim for the value of Postmodern architecture at a moment when it is regaining currency in both disciplinary and popular discussions of postwar architecture. Yet despite the renewed openness of some contemporary practitioners to referencing history and to discussing the impact of Postmodernism on their own work, the period faces preservation difficulties that do not plague the Modernist legacy. For one thing, the movement — with its oft-obscure historic references and its turn to conservatism in the 1980s — remains both misunderstood and unappreciated by the public. For another, the relative youth of many Postmodern masterpieces means that many cities have only just begun to consider them for landmark designation. In addition, as Paul Makovsky points out in Metropolis Magazine, there’s pushback within the profession: “It will be a challenge to draw attention to these structures, considering the many baby boomer architects who rebelled against Postmodernism in their youth, and might now be loath to protect buildings and landscapes from that era.” Still, Makovsky notes, a younger generation of architects is starting to take on the challenge of ameliorating Postmodernism’s legacy. The National Trust would do well to pay attention.