Architect Allan Greenberg moved his principal office to Washington a decade ago partly out of admiration for Pierre L'Enfant's bold, 200-year-old plan for the city.

Greenberg is a man of tenacious mind and strong convictions. His interest in the plan led him to poke around in the city's history and he discovered, somewhat to his surprise, that "it is but a short step" from the L'Enfant plan to George Washington's Mount Vernon.

The 60-year-old architect, born and raised in South Africa, a naturalized U.S. citizen who admits to crying at the New England town meeting where he first saw democracy in action, came to believe that the very greatness of George Washington's other deeds obscured his important role in the planning of the capital, and prevented appreciation of his genuine merits as an architect.

Greenberg's research led him to write a just-published book with a definitive title: "George Washington, Architect." Greenberg in effect has become the impassioned champion of two Washingtons--the architect and the city he helped to create.

This may indeed be the year, the 200th anniversary of Washington's death, that the great man's architectural accomplishments and visions for the capital city are credited once and for all.

Future historians will not be able to overlook the finely spun arguments in Greenberg's book. Nor will they be able to ignore the revelatory exhibition showing Washington as architect that opened the year at the Octagon Museum, or dismiss the copious supporting evidence presented by historians Robert F. Dalzell Jr. and Lee Baldwin Dalzell in "George Washington's Mount Vernon," a fine book published late last year.

One of the challenges in dealing with Washington as an architect is his silence on the subject. In his voluminous public and private papers, references to architecture--his own or that of others--are almost nonexistent. Historians therefore tended to assume that Washington was not all that interested in architecture. The rudimentary quality of the few architectural drawings from his hand were taken to mean not only that he was untrained, but also that he lacked vision and skill.

Wrong on all counts, say Greenberg and the Dalzells. Washington inhabited Mount Vernon from 1754 to 1799 but was away on public business for 20 of those 45 years. Yet no matter what the distraction--commanding an army, forming a nation--Washington wrote regularly to Mount Vernon's temporary caretakers about the affairs of the estate, going into great and almost obsessive detail in hundreds of letters.

A careful reading of the correspondence, these revisionists persuasively argue, proves not only that Washington loved Mount Vernon, farming and Virginia family life, but also that he pursued a consistent vision for Mount Vernon over a period of many years. In other words, Washington designed the house, the outbuildings, the roads, the plantings and the five subsidiary farms that made up Mount Vernon, and he did so brilliantly.

A distinguished practicing architect, Greenberg is a classicist who says the unity of nature and the man-made at Mount Vernon has influenced his own architecture in profound ways. (Greenberg's best-known local projects are the State Department's Treaty Room and office of the secretary of state; all of his works reflect the conviction that classical architecture continues to be the most humane approach to building.)

This professional experience gives Greenberg's analyses a particular authority. As an architect with a disciplined eye, he is especially sensitive to intentions that are stated visually, rather than verbally.

For instance, the asymmetry of all four of Mount Vernon's facades--unusual in the high-style architecture of late-18th-century Virginia--has often been interpreted as a sign of Washington's lack of design sophistication, at best, or sheer carelessness. Not so, says Greenberg.

Aided by illustrations keyed to the text--Tim Buchanan's excellent color photographs, period images and meticulous delineations by architects in his office--the architect-author patiently leads us through the stages of the house's design and construction. In the end, we are convinced by Greenberg's conclusion that the asymmetry was carefully thought out.

Washington, Greenberg states, "purposely understated his design innovations and incorporated them into the composition of the house, gardens and farms in a manner so unpretentious that they seem almost unintentional."

There is certainly more to Mount Vernon than the great house on the hill. The house was the centerpiece of one of the more successful farms in the young United States. That Washington was one of the most advanced farmers of his day is well known. Greenberg argues convincingly that he also was one of the great landscape architects of his time, that he planned each part of his plantation to connect with other parts in a precise and purposeful manner.

"At Mount Vernon," Greenberg writes, "Washington created a very subtle idea of order . . . a carefully composed balance between symmetry and asymmetry; between farms and gardens; between the man-made and the natural; between geometric clarity and picturesque variety; between stillness and motion; between art and life."

Furthermore, Greenberg and the Dalzells agree, the ensemble was intended as a symbolic summation of Washington's deepest and most cherished political convictions--a paradigm of what Washington once referred to as a "Republican Stile of living." The Dalzells believe that Washington's last will, in which he freed his slaves and divided the property into many pieces, was the conclusive chapter of this political statement.

It is often said that great clients make great architecture. This means at the very least that without the client's money and encouragement, many a great building would not exist. But in the best circumstances, the aphorism implies a more collaborative process in which the client and the designer share certain fundamental values.

In the second section of this book, Greenberg makes a strong case that Washington was the great, indispensable client behind the planning of Washington, D.C.

It isn't simply that without Washington, the L'Enfant plan would not exist, though that is certainly true. Washington personally chose L'Enfant over others, most notably over Thomas Jefferson, his secretary of state. Rather, in Greenberg's view, the plan reflected Washington's own beliefs about the future of both the new city and the new nation. Whether the president actually helped to shape L'Enfant's plan is unknown, but Washington responded strongly to its ambition and its symbolism. He and L'Enfant thought exactly alike on both scores.

Greenberg's recounting of this inspiring yet melancholy episode--Washington refused to turn his back on the plan even after he reluctantly dismissed the brilliant Frenchman--is quite moving. It is also one of the best essays ever written on the democratic meanings of the L'Enfant plan, which, Greenberg states, "is one of the great benchmarks in the history of city planning."

"George Washington, Architect," by Allan Greenberg, published by Andreas Papadakis, 168 pages, 130 color plates, $55.