For nearly a century and a half after L'Enfant created Washington's plan, the city's architecture was styled using visual languages derived directly from Greek, Roman and medieval precedents. But, during this same period, despite the prevailing classical and romantic currents of fashion, there were designers elsewhere pursing new, historically unprecedented directions.

For the first great international exposition in London in 1851, engineer Joseph Paxton designed the Crystal Palace in Hyde Park.

This gigantic, factory-made, cast-iron and glass structure foretold a new age of building unencumbered by the necessity for heavy, load-bearing masonry walls. Its Victorian decoration was visually subordinate to the translucence and transparency of its lofty vaulted roof and membrane-thin walls of glass, its soaring skeletal framework and the exhibits it contained -- arts and crafts on the one hand, tools and machines on the other.

Eiffel built his tower in Paris for the 1889 French centennial, again demonstrating new design potential and fabrication techniques that bore little stylistic or technical relationship to antiquity.

The Eiffel Tower and Crystal Palace were rationally engineered, yet romantically inspired architectural feats whose first appeal was dramatic and sensual, like a Gothic cathedral, not subtle and intellectual, like a Palladian villa.

One hundred years ago in New York City, the Brooklyn Bridge was being suspended by cables across the East River. Even while the pointed arched openings in its masonry support towers paid homage to Gothic revivalism, it foretold the future of lightness and steel and systems management. New mechanical building tools and machines were being perfected, Otis' elevator among them.

During the decades immediately before and after 1900, both European and American thinkers -- philosophers, social critics and scientists, as well as artists and architects -- were convinced that utopia was at hand.

The 20th century was the ultimate future. Unprecedented technological, social, economic and political achievements would ensure the attainment of liberty, justice, prosperity and happiness for all the world's peoples.

Questioning tradition and ever ready to embrace such utopian trends, some architects condemned stylistic revivalism and the tedious reuse of ancient motifs. They believed them to be costly and meaningless, outmoded symbols irrelevant to the values and experiences of the new culture. It was again time for change.

In the American Midwest, architect Louis Sullivan, foremost representative of the late 19th century "Chicago School," was designing buildings clearly signaling the advent of modern architectural thought. His Wainwright Building in St. Louis (1891) and Carson, Pirie, Scott department store in Chicago (1904) rose many stories and were supported entirely by prefabricated metal skeletons. Exterior walls were only an infilling and covering curtain separating inside from outside. They supported nothing but their own weight.

Windows became much larger, admitting more light as they stretched almost from floor to floor and column to column. The imprint of the skeletal frame on the facade became a dominant expressive characteristic. The resulting interior spaces, interrupted only by grids of relatively slender columns, were multi-directional and infinitely subdividable by optional partitions. Internal vertical shafts contained stairs and elevators. Here was a new style and a new kind of real estate, liberated from the conventions of stone technology and masonry wall imagery.

But Sullivan and others were worried. Commenting on the 1893 Columbian Exhibition with its stage-set, "mercantile classicism" of plaster, he predicted that "damage wrought to this country by the Chicago World's Fair will last half a century."

Washington certainly proved him correct about the fair's influence. In 1894, architect and developer Thomas Franklin Schneider built the Cairo on Q Street. Among the first high-rise, steel-frame apartment buildings in the country, its 160 feet of height offended neighborhood and city residents. It prompted D.C.'s unique and vital height-limiting zoning ordinance, but it also reinforced the city's propensity for classicism.

After the turn of the century, Sullivan's disciple Frank Lloyd Wright likewise staked out the Midwest with buildings having little or no European precedent. Seeking a non-derivative, anti-revivalist, honestly native American architecture, Wright condemned "the styles" and evolved his own highly personalized design philosophy and formal language. While the Chicago School advocated technological and functional appropriateness ("form follows function!") with its significant implications for future urban real estate, Wright primarily explored the nature of single buildings wedded to the landscape.

His "organic" architectural legacies -- freely flowing space, visual integration of inside with outside, emphatic expression of horizontal planes, abstract geometrical decorative patterns and buildings shaped by the circumstantial pressures of site and climate -- strongly influenced contemporary architects.

However, few were willing or able to emulate his style literally. One sees little of Wright in Washington's architecture except indirectly.

At Princeton University in 1930, Wright discussed his contempt for the classic cornice, so beloved in D.C. Citing the roof collapse at the neo-classical Wisconsin State Capitol as symbolic, he characterized the cornice as the image of a "dead culture," useless by comparison with a genuinely protective overhanging roof. To him, a cornice was an "'embalmed" marble vestige of an originally wooden Greek temple having no place in an architecture for 20th century democracy. Few Washingtonians shared his viewpoint.

Meanwhile, Wright's European counterparts developed alternative manifestos. The Bauhaus movement in Germany, led by Walter Gropius, combined 1920's interests in building craft, engineering and economic efficiency, social and political reform, and constructivist art to create a new "international" style of architecture. Like zealous classicists, Bauhaus adherents espoused utopian ideals of public welfare, truth, objectivity and logic.

This meant a totally new architecture for the future: honest use of modern materials, especially steel, concrete and glass; open, flexible plans; elimination of non-functional decoration and systematization and standardization of construction. Architectural beauty, they avowed, would result naturally and inevitably from a rational process of analysis, composition and building, but without applique and allusion. They were convinced that a universal, culturally neutral mode of architectural expresion (hence the label "international") would supersede individualistic, historicist manifestations of style, taste and tradition.

Moreover, new 20th century architectural challenges awaited, since the great war was over. Instead of churches, villas and civic monuments, architects would be designing industralized housing for the middle classes, soaring curtain-walled office buildings, assembly-line factories, mercantile centers, airports, hospitals and even entire cities. These projects would be complex and socially interventionist. The architectural styles of the past seemed especially inappropriate and pretentious for such revolutionary and optimistic times. The individual and the collective could at last coexist.

Aware of all of these movements, many American architects still adhered tenaciously to the Beaux Arts tradition, particularly in Washington. How ironic that monumental classicism, proclaimed as the appropriate symbolic architectural style by Stalin, Hitler and Mussolini for each of their respective realms, was also adopted by capitalistic democracies as the style most befitting public edifices and banks.

Nevertheless, during and after the depression era of the 1930's, Washington's passion for tradition and historicism would be cooled by the arrival of Art Deco and Art Moderne. A few architects and clients would finally be influenced by the rationalist, stripped classicism of pre-war Italy, the international styles imported from Germany and its neighbors and the compositional innovations of a Swiss-born French architect, Le Corbusier.