Visualize the living area of architect Arthur Keyes's Washington house, circa 1950: slightly angled ceiling with inset chrome-plated light fixtures, broad picture windows on two sides, white-painted end wall with floating shelves on metal rods, side chairs by Charles Eames, a lounge chair bent to the body's shape in laminated plywood, gray wall-to-wall carpet, dining table in Scandinavian wood and style, simple brass chandelier hanging like a mobile.

This telling image was one of the first in a slide show of early works Keyes and David Condon gave for colleagues a few weeks ago. The presentation extended through the lunch hour, much longer than planned. "A lot of the people had been here only five years," Keyes said later. "They had never seen this stuff."

Keyes, at 75, is set to retire. Condon, 76, already is listed as emeritus. Next fall the firm's lengthy name -- Keyes Condon Florance Eichbaum Esocoff King -- will be officially shortened by two. It's a passage worthy of note, encompassing half a century of Washington's architectural history and a good part of the story of modern architecture here.

Keyes's name is linked to the founding of the firm, in 1950, and Condon's to its first major reorganization in 1956. But the genealogy dates to wartime Washington and back, even, into the New Deal. The firm's initial name was Keyes, Smith, Satterlee & Lethbridge. Along with Nicholas Satterlee and Francis Donald Lethbridge, Keyes had come to the capital as a naval officer during the war. The other founding partner, Chloethiel Woodard Smith, had arrived from the West Coast during the first Roosevelt administration, a young architect (and rare woman in the field back then) attracted by the new federal housing programs.

Condon too was deposited in D.C. during a wartime Navy tour. He had hooked up with Washington architect Charles Goodman during the war and, afterward, had worked with him on the design of houses in Hollin Hills south of Alexandria, the Washington area's first modern suburban enclave. He left Goodman in 1952 to join KSS&L, which became Keyes Lethbridge & Condon four years later when Smith and Satterlee departed to organize their own practice.

The common denominators in the collective story are an affection for an adopted city and a devotion to modern architecture. At architecture schools during the Depression the future partners had imbibed an impatience with things as they were and a desire to create something untainted by the past. After the war, like many in their generation, they were anxious to put their enthusiasms to work for like-minded clients, builders and designers.

Keyes and Satterlee, for instance, worked for the local firm of Berla & Abel in the immediate postwar years. Joseph Abel was, of course, the architect of many of the city's most distinguished modern apartments, those civil blond brick buildings with the vertical casement windows along Connecticut and Wisconsin avenues. But the experience was not wholly satisfying, Keyes recalled: "You punched a clock at 8:30 every morning, you went to your drafting table and you didn't look up."

The postwar building boom in city and suburbs provided fertile ground for start-up architects. "There was a tremendous backlog of building to do," Keyes reminisced, although "in the beginning we were just a bunch of youngsters doing little budget projects." The projects, mostly, were houses in the close-in suburbs. A few were custom-made jobs, but the great majority were subdivisions. In the long run the firm in its various permutations designed nearly 2,500 houses for private developers in the Washington area.

What were they like, these early postwar homes? "Colonial"? Most certainly not. The partners disdained what they viewed as historical affectation and rejected many a commission where it was called for. They discovered a market niche and thought of it as the wave of the future. "Actually," Keyes reflected, "we didn't have much competition in terms of modern architecture."

Were the homes "industrial" -- prefabricated? No. Like many in their generation, having witnessed firsthand the mighty industrial organization that fueled the American military operation, these young architects believed, as Condon recalled, "that the housing industry would be revolutionized" after the war. That this revolution did not happen was a disappointment the partners shared with modern architects worldwide. (They experienced the disappointment twice, in fact. A competition-winning KL&C proposal for 4,500 prefab units at the Fort Lincoln "new town in town" in Northeast Washington during the late '60s, spurred by the Johnson administration's "Operation Breakthrough," likewise came to naught.)

But were they economical, these Keyes group projects? Yes, indeed. Constructed mostly of wood in modular units, with carports, clean lines, minimally peaked roofs and lots of large windows for views and light, they were modest, straightforward, unencumbered affairs built for the mobile modern life. Like Keyes's living room, they were totally lacking in pretension. When financed by veterans' loans they cost next to nothing. Asking prices for the houses in the Pine Spring development off Route 50 in Virginia were between $15,000 and $20,000.

And, by the standards of the time, these subdivisions were conscientiously planned. There were in those years practically no sensible restraints on the construction of single-family houses in the burgeoning suburbs. Common practice was simply to bulldoze the land and apply a familiar pattern of curved and cul-de-sac roads on the flattened terrain. Like conventional developments, the KSS&L and KL&C projects were self-contained, lacking commercial services and linked only to major arterial roads -- a prime cause of today's suburban traffic jams.

But in their aesthetic and ecological sensitivity, developments designed by these architects were exemplary. Consciously working in the suburban tradition of Ebenezer Howard, the turn-of-the-century English "garden city" theorist, and American landscape architect Frederick Law Olmsted, they were attentive to existing slopes, ground cover, water flows, trees and the positioning of each house. "I sited each one myself," Lethbridge once said of the Pine Spring homes. "We always made sure we got to the road layout before the traffic engineers," Condon quipped.

Though it seemed the most natural thing to do at the time, the firm's concentration on larger-scale projects was not the usual pattern for young architects. "We did some small stuff on the side for family and friends," Condon said, "but basically we started right out planning large projects, looking at fairly big areas of the city." This is one explanation for the extraordinary resiliency of the firm. Its experiences in the suburbs assured that it was well positioned to take advantage of changes in the local market, such as the move to major urban renewal plans in the '60s or the focus on big commercial buildings in the '80s.

KL&C, for instance, designed two of the bigger residential projects in the new Southwest, and Smith and Satterlee, after they left the firm, also designed large chunks of this urban renewal area. The major faults of Southwest, including the immense social costs of population displacement and the empty plaza syndrome, are attributable more to the overall plan than to the separate pieces. In any case, the KL&C projects -- Tiber Island and Carrollsburg Square -- are handsome, adroitly composed combinations of row houses, massive apartment buildings and open spaces.

Conceptually, however, the firm's best urban residential work is the Columbia Plaza development on 23rd Street NW. Although substantially disfigured by the later addition (by another architect and developer) of an ugly, out-of-scale office building, and harmed by the impecunious detailing of its plaza, it remains one of the city's premier mixed-use, modernist enclaves. The serpentine "wall" of row houses above a freeway stands as an impressive -- and very livable -- reminder of the short-lived popularity of "Brutalist" architecture.

Among other notable modern buildings by the firm are the Pepco substation in Southwest -- the finest postwar industrial structure in the city -- and the Sunderland Building, at 19th Street and Sunderland Place NW. The latter, sheathed in precast concrete panels framing deep, narrow window openings, is, like Columbia Plaza, clearly indebted to the late work of Le Corbusier, the modernist giant. And yet it's not a standout statement, not stressful, not inspiring. To the contrary, it's a modest, comfortable, urbane building that fits its narrow city street.

Formal innovation and theoretical inventiveness were not the firm's strong suit in its modernist years. Civility was -- that most characteristic, if slightly boring, Washington architectural virtue. The Sunderland, completed in 1969, is a very civil building in an almost up-to-date style. And it was, strictly speaking, one of the firm's last modern buildings.

In 1978, after enduring a recession and going through another organizational change at the top (Lethbridge went out on his own in 1975, replaced by Colden Florance), the firm submitted a competition entry for the Alexandria waterfront, and won. A splendid exercise as both urban design and urban architecture, it was a key transitional work.

Alone among the competitors did the firm -- Keyes Condon Florance by then -- propose to transform the place by saving World War I vintage torpedo factory buildings. Surprisingly, perhaps, vintage modernist Keyes was at the head of the design team, proposing not only a very lively remodeling of those industrial Goliaths but also a Victorian revival restaurant at the far end of a pier. "I got a lot of heat for it," he recalled, "but nothing else felt right at that spot."

The rest is a better-known story. From that time forward the firm has turned out a plenitude of sophisticated commercial and public buildings, each different in style, many involving historic preservation, and the best always distinguished by an inventive reading of the architectural context. Among the best: 1100 New York Ave. NW, incorporating the old Greyhound bus terminal; 2400 Pennsylvania Ave. NW, a vivid mix of modern and pre-modern elements; and Republic Place at 1776 I St. NW, one of the city's new bell-tower buildings.

Florance sees quite a bit of continuity despite the stylistic and generational breaks. "The firm has always been aware of the best architecture going on around the country, and has been responsive to that," he said. "And its always been strongly contextual. It's just that we began to see that the job could be done in a somewhat more literal way and still be fresh."

Still, the influence of a younger generation of designers is clear -- Thomas Eichbaum, Philip Esocoff and David King, along with partners Bruce Dicker, Tam Nguyen, Mark Maves and Russell Perry, joined the firm in the late '70s and early '80s. Elevating this generation to power "was simply an orderly process for keeping talented people," explained Keyes. "Usually the old boys hang in there and the younger generation gets discouraged and then the firm dies," added Condon. "Nothing goes on."

Come September, when KCFEEK becomes FEEK, Florance, who did a summer stint with KSS&L back in 1954 and who joined KL&C in 1962, will remain as the last link to the firm's past. But by the time he departs in a decade or so, the youngsters will have been there for nearly a quarter of a century.