Two generations ago, preservation was a subject more likely to be discussed genteelly in the tastefully appointed drawing rooms of those with the means and leisure time to pursue the subject, rather than an issue of public debate, planning and financial interest. Since then, preservation has become a popular subject whose roots are as diverse as the interests of our society.

As with other social movements of the turbulent '60s, the popular preservation movement was spawned in frustrated reaction to the loss of handsome buildings and landscape for drearily monotonous speculative development. We preservationists have been vociferous, often abrasive and even occasionally abusive. During the past 25 years, we have gradually grown to realize that litigiousness and obstructionism are ultimately counterproductive and that much more can be gained for everyone by hearty cooperation rather than adversarial stances. Tax advantages, development swap-offs, incentives and esthetic sensitivity have begun to go hand in hand with scholarship, fiscal sensibility, historic districts and a recognition of the need for cash flow and the profit motive. Preservation has become good business that welcomes investors to produce a better community.

Although the last 25 years have included many important preservation projects -- Congressional Cemetery and the graduate student library of Georgetown University's Healy Building, to name just two -- the following are 10 of the most memorable "saves" of those years.

The most important preservation project symbolically in Washington is the retention of the Olmsted Terraces and the restoration of the U.S. Capitol west front. The east front was lost in 1960 when a new marble copy of the original was built in front of the old in order to create additional office space. Since that time there has been a running battle -- between preservationists and members of Congress who wanted even more exclusive offices -- over a similar "extension" of the west front, which is the last surviving facade of the original build-ing. Aside from the issue of preserving the last remnant of the original Capitol, the proposal would have irreversibly altered the carefully studied balance between the Capitol and the late 19th century terraces leading to the Mall. The terraces and the surrounding landscape were designed by Frederick Law Olmsted, the founder of the profession of landscape architecture and the preeminent designer who was responsible for Central Park in New York. His design has become the very image of the country, and its irreparable loss would have been a national esthetic and historic tragedy. In 1983, after a generation of debate, Congress came down firmly and decisively in favor of preservation and the work is now under way.

UNION STATION, designed by Daniel H. Burnham of Chicago in 1908, was based on monumental ancient Roman baths. But by the 1970s, railroads were dying out and this extraordinary entrance to the city was deteriorating and largely unused. With the proposal to turn Union Station into a "Visitor Center," the terminal was relegated to new, low-ceilinged cramped quarters at the rear; most of the tracks and their columned sheds were destroyed; a still uncompleted parking garage was begun; and the floor of the enormous vaulted waiting room was gutted for an oversized projection pit where one could see slides of famous Washington buildings. But all the visitor needed do was walk out the door to the real thing! Having barely survived its earlier rehab, restoration of this extraordinary public space is in progress.

PENNSYLVANIA AVENUE almost succumbed to ill-conceived 1960s proposals. Following the Kennedy inaugural, there was a movement to improve the avenue. From the planning boards came a plan for a Mussoliniesque super- aggrandizement that would have warmed the heart of Albert Speer. Among other serious aspects was the destruction of the 1890s Old Post Office in favor of completing the 1930s Federal Triangle, and the demolition of Henry Hardenbergh's 1901 Willard Hotel for an enormous wind-swept plaza. The newly created National Foundation for the Arts and Humanities joined forces with preservationists for the successful renovation of the Old Post Office as an exciting public place of shops, restaurants and federal offices.

The Willard Hotel has had a more difficult time of it since its closing after the 1968 riots. There's been a Willard Hotel on the site since 1850, but for a while it seemed that it would disappear forever or be converted into an office build commercial skin. A more enlightened Pennsylvania Avenue Development Corp. cooperated with a succession of developers and architects until Oliver T. Carr accepted the challenge to sympathetically enlarge and restore this "Hotel of the Presidents," as a hotel. The restoration of the interiors promises to be a true celebration of the artistry so prevalent at the turn of the century.

IN 1975 architects and scholars banded together here to act upon the suggestion of noted Washington architect Chlothiel Woodard Smith that the Pension Building would admirably serve as a museum devoted to the arts and crafts of the American construction industry. At the time, the Pension Building was used by the local courts and was deteriorating badly. The suggestion for its adaptive reuse and restoration seemed so right that Congress, scholars, professional designers and the construction industry joined forces and in 1985 the National Building Museum opened to the public.

LOGAN CIRCLE (originally Iowa Circle) was one of the handsomely landscaped Victorian urban parks about which were constructed exuberantly grand homes. By the late 1960s, the area was a derelict red-light district, with a once heavily treed circle pared away to a lemon for the ease of high-speed commuter traffic. To the credit of the D.C. Department of Transportation, which cooperated with the citizens who bought into the burned and gutted neighborhood, the circle has been returned to its original configuration, landscaped and treed. The homeowners have invested as much sweat equity as cash, and the city now profits by a more stable and increasingly attractive family-oriented neighborhood.

MERIDIAN HILL PARK was begun in 1920, and was built according to the designs of landscape architect George Burnap and architect Horace Peaslee. To ascend from the lower Italian gardens to the upper French parterres is to experience hundreds of years of European design development. But in the 1970s concrete was deteriorating; fountains and cascades were seldom, if ever, operable; and the scruffy once-grand park was a haven for criminals and drug dealers. But the National Park Service has undertaken restoration here. Most of the fountains are now in working order, structural repairs are under way, and plant maintenance has begun to return to the public an exhilarating pleasure garden.

SOME PLEASURABLE places in the city are available to us not because of restoration activity, but due more to what might be called "benign neglect." That is, we have either the good sense to leave well enough alone or the area has not become fashionable enough to attract development attention. Washington abounds with such sites as Sheridan Circle, Swann Street and LeDroit Park. These neighbor hoods show that preservation does not necessarily mean enormous infusions of money or reconstruction. Sometimes we need only to jealously guard what we already have to insure no losses -- that is the easiest and greatest "win".

A genuine sense of community can now be found in Washington and is one of the major reasons that so much preservation activity has arisen in the past 25 years. We have begun to realize that more is to be gained for everyone by constructive, responsible, cooperation.