The cause was Alzheimer’s disease, his wife, Anya Robertson, said.

The scion of an aristocratic Virginia family, Mr. Robertson designed a wide range of buildings in multiple styles, but he never lost his love of classicism, which he called “the symbolic hard currency of architecture.”

“It’s gold in the bank,” he said in a 1996 interview with Town & Country magazine. “The other stuff is leveraged buyouts and soybean futures.”

Mr. Robertson first came to public notice not as an architect of individual buildings, however, but as one of the eager and ambitious young designers who clustered around John V. Lindsay when he was elected mayor of New York in 1965.

Mr. Robertson came up with the notion of a cadre of architects who would turn their design skills to public service. He convinced Mr. Lindsay, whom he had met through the mayor’s wife, Mary Lindsay, a fellow Virginian, to establish the Urban Design Group, a special municipal agency intended to help the mayor raise the level of public design in the city. The group included the architects Richard Weinstein, Alexander Cooper, Jonathan Barnett and Myles Weintraub.

Mr. Robertson later served as the first director of the Mayor’s Office of Midtown Planning and Development, whose projects included devising zoning provisions that allowed new skyscrapers to house a mix of offices, apartments, retail stores and, in the case of the theater district, new Broadway theaters.

To Mr. Robertson, there was no inconsistency between his love of grand classical architecture and his passionate belief in cities: It was all about finding ways to turn time-tested ideas to the benefit of modern life, and he would spend much of the rest of his career promoting better urban design.

“I think architects, having abrogated the role of designing cities, are to blame for the cities that we have, which are a real mess,” he said at a conference at the University of Virginia in 1982. “Architects must have in front of them some notion about the order of the whole, not just the parts.”

 After a stint with the New York City Planning Commission, Mr. Robertson worked briefly for Arlen Realty in New York, helping to develop Olympic Tower in Midtown, one of the first mixed-use skyscrapers to emerge from the regulations he had shaped.

In 1975, he accepted an invitation from the shah of Iran to move to Tehran to design a new city, Shahestan Pahlavi, in which he sought to integrate elements of traditional Persian design into modern architecture. The project was never built — it was cut short with the fall of the shah in 1979 — and Mr. Robertson returned to the United States.

Over the next decade he divided his time between New York, where he established a practice in partnership with the architect Peter Eisenman, and Charlottesville, Va., where he served as dean of the architecture school at the University of Virginia. For years he resided on the university’s campus, which was designed by one of his heroes, Thomas Jefferson.

When he stepped down as dean in 1988 and returned to New York full time, he and Mr. Eisenman, a confirmed modernist, parted ways, and Mr. Robertson formed a new partnership with Alexander Cooper, his fellow Lindsay alumnus, to form Cooper Robertson and Partners. Now called Cooper Robertson, the firm continues to have a large national presence as a designer of schools, university buildings, civic structures and museums.

Mr. Robertson played an active role in many of the firm’s larger projects, including the design of Celebration, Fla., the new town developed by Disney near the company’s theme parks; WaterColor, another planned community, on the Florida Panhandle coast; and portions of New Albany, Ohio, an upscale suburban community outside Columbus developed by the retail mogul Leslie Wexner.He also maintained a popular practice as an architect of private residences. He was known for designing houses for prominent clients that were both elaborate and understated and evocative of older structures without being directly imitative of them.

His clients included the financiers Henry Kravis and Leon Black, both of whom commissioned him to design multiple houses; the record producer Ahmet Ertegun and his wife, Mica Ertegun; Alfred Taubman, the shopping center builder and owner of Sotheby’s; Don Hewitt, the CBS News producer; and Marshall Rose, the New York developer and philanthropist.

The house he designed for Mr. Rose in East Hampton won a national design award in 1991 from the American Institute of Architects; at the same time, another of Cooper Robertson’s projects, the design for Battery Park City in Lower Manhattan, won one of the institute’s urban design awards. Cooper Robertson was the first architecture firm to win national awards for both architecture and urban design in the same year.

Mr. Robertson was awarded the Thomas Jefferson Medal in Architecture in 1998 and the Driehaus Prize, an international award for distinction in traditional architecture, in 2007.

Jaquelin Taylor Robertson was born in Richmond, Va., on March 20, 1933. He was named for his grandfather Jaquelin Taylor, who founded Universal Leaf Tobacco, now the Universal Corporation. His father, Walter S. Robertson, a diplomat, was John Foster Dulles’s assistant secretary of state in the 1950s and played a central role in shaping the Eisenhower administration’s anti-Communist China policy. His mother was Mary Dade (Taylor) Robertson.

The year Jaquelin was born, his father commissioned the prominent architect William Bottomley to design a 20th-century version of a great classical mansion for the family. The house, Milburne, which was completed when the boy was 2, would become one of Richmond’s most prominent estates, and growing up in the house gave him not only a lifelong admiration for traditional architecture, but also a sense that classical buildings were compatible with modern life and not just relics of the past.Jaquelin’s childhood years were divided between Virginia and China, where his father served as a special envoy in the Foreign Service in the 1940s. The sprawling urbanity of Beijing would come to have as great an influence on Mr. Robertson as his family’s genteel estate in Virginia had.

“I am a child of two architectural settings,” he said years later, “one a provincial, rural, Anglo-American, Georgian-Palladian one, the other an exotic, foreign, imperial and highly cosmopolitan one.”

He graduated from Yale in 1955, and spent two years at Magdalen College at Oxford as a Rhodes Scholar. Back in the United States, he returned to Yale and enrolled in its school of architecture, from which he graduated with a master’s degree in 1961. He moved to New York and started his career working for the architect Edward Larrabee Barnes, where he remained until his encounter with Mr. Lindsay led him to think about architecture in terms of public service.

Mr. Robertson married Anya Sonn in 1964. In addition to her, he is survived by his sister, Catherine Claiborne.

Even when he returned to private practice, Mr. Robertson was reluctant to see architecture primarily through a commercial lens. Courtly and elegant in his dress, he reveled in the intellectual discourse of the academic side of the profession as much as the public discourse of the civic side.In his Southern drawl, which he never lost, he would lecture real estate developers on their responsibility to build structures that would enrich the city and not just their own pocketbooks.

As dean of the architecture school at the University of Virginia, he convened in 1982 a private meeting of 25 of the world’s leading architects in the Jefferson-designed campus Rotunda, where they presented their work and engaged in sharp criticism. The event, which was recorded and transcribed into a book called “The Charlottesville Tapes,” was attended by Philip Johnson, Frank Gehry, Robert A.M. Stern, Tadao Ando, Kevin Roche, Rem Koolhaas and Cesar Pelli, among others.

Mr. Robertson took issue with what he saw as his colleagues’ obsession with parochial concerns. He was struck, he wrote later, “by how cut off we as architects are from the world around us.”

“This seems particularly true of the ‘thinking architects,’” he wrote. “We don’t seem to understand very well yet how our society works or what our people want or need, and we are continually caught up in a kind of Alice-in-Wonderland situation of either giving answers to questions no one is asking or ignoring completely some of the more pressing and obvious problems.”

Jefferson remained a touchstone for him. “On the Sunday after the conference a small group of us made an early morning pilgrimage up to the ‘little mountain,’ Monticello,” he wrote, “and there, in the clear, cold air of the November morning, we were able to look out over what had been the wilderness promise of the New World and to experience again the mystery and power of the architectural statement — of the ‘built idea.’”

Mr. Robertson was a member of SAH through 2002.  

Robert A.M. Stern remembers Jaquelin Taylor Robertson here.