The architecture world has a habit of paying homage to its greats on their centenaries. Architects rarely live long enough to enjoy the celebrations, but since Chinese-American architect Ieoh Ming (I.M.) Pei is still alive, the mood at the National Gallery was light last week when the museum celebrated his 100th birthday with a lecture in his honor. This was a real birthday party, although he wasn’t in attendance.

Pei did not build as much in Washington as in New York, and he is probably best known for his work in three other cities: his renovation of the Louvre in Paris, the John F. Kennedy Presidential Library in Boston, and the Bank of China Tower in Hong Kong.

But over a career so long, he was bound to leave his imprint in D.C. His two most significant projects here are perceived in opposite ways. The East Building of the National Gallery is heralded as a masterpiece; L’Enfant Plaza is written off as a failure. Surprisingly, the projects were designed back-to-back.

L’Enfant Plaza opened in 1968, the same year Pei received the commission to extend the National Gallery. By this time, the redevelopment of Southwest D.C. and the area along 10th Street SW in particular had occupied him for a long time as different urban-renewal schemes proliferated and federal and local officials battled over where to put a new cultural center—the future Kennedy Center.

Pei and his client, the developer William Zeckendorf, had been working on plans since the mid-1950s, but construction didn’t begin until 1963, and by that time a lot had changed from the original vision. The cultural center would be in Foggy Bottom, not on 10th Street, and the number of office buildings had shrunk. Meanwhile, Zeckendorf’s real-estate empire was wobbling, and he had to sell his interest in the project shortly after construction began.

Like other designers in that period, Pei believed that a grand scale was appropriate for the nation’s capital, and that new, rationally planned districts with generous open spaces would help cities compete with the suburbs that were sucking people and dollars out of downtowns. We know with hindsight that this approach was flawed. Today, 10th Street is absurdly wide in proportion to the surrounding buildings and in relation to its dead-end terminus, Banneker Park.

And L’Enfant Plaza is a dead zone, an overscaled void where you expect to see tumbleweeds blowing through at night or on weekends. But the 1957 Zeckendorf-Pei plan shows a much more lively L’Enfant Plaza than the one that was eventually built, with an opera house and outdoor restaurants. It’s also worth noting that Pei was not responsible for the unfortunate Forrestal Building, which blocks the view to the Mall. In fact, he fought against it.

The buildings at L’Enfant Plaza by Pei’s deputy Araldo Cossutta are handsome, reminiscent of the hooded, desert-toned towers Pei designed for the National Center for Atmospheric Research in Colorado, as well as his University Village cluster on the campus of New York University. Likewise, the four apartment buildings in Town Center Plaza, a complex that Pei designed for Zeckendorf during the L’Enfant wrangle, are sleek and well-proportioned. Two have been sympathetically restored by Washington architect Phil Esocoff.

Pei was moving on from being Zeckendorf’s architect, with several admired projects under his belt, when the National Gallery became interested in him in the late 1960s. Congress had set aside the site east of the original gallery for an addition, but its trapezoidal shape was a challenge. Pei came up with the solution in a back-of-the-envelope sketch. He proposed a large isosceles triangle fitted against a smaller right triangle.

Credit: Photo courtesy of Lance Couzens/Flickr

What Pei accomplished on the Mall, as the National Gallery’s Susan Wertheim said in her birthday lecture, is a perfect rapport “between a modern, classical building,” i.e. John Russell Pope’s 1941 temple, “and a classic modern building,” or the new H-shaped wing across the courtyard. With the constant support of Paul Mellon, the chairman of the gallery’s board, Pei could finesse details like the warm pink limestone (mined from the same quarries as the West Building), the pleated space frame over the atrium, and an escalator bank gently scooped out of the wall.

Anyone who doubts that modern architecture inspires awe and affection should walk to the “knife’s edge” on the building’s southwest corner, where two walls meet at an impossible 19-degree angle. The edge has been rubbed to a rusty color over the years by thousands of inquiring hands. So has Pei’s name, inscribed in the atrium.

In a 1987 interview, Pei said that he was proud of his urban renewal work, but that it was limited as an art form. “The exploration of form, the exploration of space is something you have to find in other types of architecture, like museums,” he said. There are many more constraints on a designer working on an urban district plan than on a single art gallery, and that can make it hard to reconcile the two types of effort. But the “real” I.M. Pei is not necessarily the artist who insisted on his 19-degree corner. Both L’Enfant Plaza and the NGA reveal another talent of Pei’s, as a mentor to, and collaborator with, other designers.

At L’Enfant, Pei delegated the two office buildings to Cossutta, who became an accomplished architect in his own right. (He passed away in February.) At the National Gallery, he assigned significant design work to an employee named Yann Weymouth, who also went on to have a long and successful career. Pei formed an enduring partnership with his younger employees James Freed and Henry Cobb, who gave D.C. the U.S. Holocaust Museum and Ronald Reagan Building (both spearheaded by the late Freed), among other buildings.

In recent years, Pei has consulted for his sons’ architecture firm on projects including the chancery of the Chinese Embassy in Van Ness, and he entrusted his protégé Perry Chin to lead the recent renovation of the East Building (with local architects Hartman-Cox).

Looking at Pei’s D.C. buildings through this lens is a better way to understand him—an architect of rare talent who often had to bend it to circumstance, who drank in the optimism of his time, and who greatly encouraged the contributions of his peers and up-and-comers. That’s not a bad model for the architectural profession as a whole. Happy belated birthday, Mr. Pei.