Six years ago this spring, a downtown landmark -- the McGill Building -- was razed to make way for a PMI parking lot at 10th and G streets NW.

It wasn't the first building local preservationists tried and failed to save, now was it the last. But it was one of the most important, because the wrecking ball that felled the McGill Building set in motion a process that resulted in a strong landmark protection law that took effect Saturday.

The Historic Landmark and Historic District Protection Act of 1978 empowers the mayor, upon recommendation of a review board and after a public hearing, to veto demolitions and alterations of buildings in the city's 11 historic districts or any of the city's 330 official landmarks. New construction in historic districts also will be subject to a veto.

Under the law, passed in November and signed by former Mayor Walter E. Washington in December, city officials must determine that the issuance of demolition, subdivision, alteration or building permits are in the public interest or that denial of permits will cause "unreasonable economic hardship."

A property owner who claims "unreasonable economic hardship" must submit an affidavit listing detailed financial information on the property, including any purchase offers.

The provision is designed to satisfy the constitutional requirement persons are not deprived of property without due process -- the test applied by the Supreme Court when it upheld New York City's landmark law in the Penn Central case last June.

According to a "friend of the court" brief filed by the National Trust for Historic Preservation in the Penn Central case, 530 municipalities have landmark laws.

But according to David Bonderman, vice president of Don't Tear It Down, the local preservation group that did much of the research on which the D.C. law is based, only a few cities -- including New York and Alexandria, Va., -- have landmark regulations as tough as Washington's new law.

The law replaces Reglation 73-25, an amendment to the D.C. Building Code that was passed six months after the McGill Building was demolished. Under this regulation the mayor -- or, in practice, his agent, the head of the Department of Housing and Community Development -- could, after hearings, order a 180-day delay before issuing permits to demolish or alter a structure listed on the city's inventory of historic sites, the National Register of Historic Places or in a historic district listed on the National Register.

The purpose of the delay was to permit city officials to negotiate with the owners and "civic groups, public agencies and interested citizens to find a means of preserving" the structure or site.

Before the passage of the delay regulation, the only way to save a building was through a section of the National Historic Preservation Act of 1966 that required public review of proposed demolitions of federally owned buildings or buildings involved in federal projects. This was the tool preservationists used to save the Old Post Office Building -- a crusade that gave birth to Don't Tear It Down.

Most buildings, however -- even those listed on the National Register of Historic Places -- had nothing to shield them from the wrecking ball. Finally, in the wake of the McGill Building demolition, city employes concerned with nominating landmarks to the National Register worked with J. Kirk-wood White, then an aide to City Council Vice Chairman Sterling Tucker, to draft the delay regulation.

During the 5 1/2 years the delay regulation was in effect, more than 1,200 demolition and alteration applications have been reviewed, and delays have been imposed in 25 cases, according to Acting D.C. Corporation Counsel Louis P. Robbins, who helped draft the final version of the new law. Most of the delays were simply that -- after six months most of the buildings in question were torn down.

But there were a few successes. Howard University was persuaded to preserve three Victorian houses in LeDroit Park. The Brown AME Church agreed to include two Capitol Hill rowhouses in its new educational building -- though two other houses preservationists wanted to save are still slated for demolition. A developer agreed to save three of six Victorian homes on Maryland Avenue NE slated to be razed for a condominium complex. And the Adams House, a Mount Pleasant landmark, was saved in a compromise between a developer and the community.

Most of the successful negotiations were concluded after a 1976 court decision involving the demolition of the old Dunbar High School. When the 180-day delay in demolition period ended, the school's alumni association obtained a court injunction prohibiting demolition on the grounds that meaningful negotiations had not been held and that the owner -- the city -- had not considered all possible alternatives. The school eventually was torn down -- after an additional court-ordered negotiation -- but an important precedent had been set.

"The Dunbar decision put a requirement on property owners to enter into valid negotiations," said an historic preservation official who has helped set up negotiations under the delay regulation.

An effort by a group of Dupont Circle activists to pass legislation barring demolition not only of landmarks but of all buildings used for housing got nowhere, but, according to Leila Smit, a founder of Don't Tear It Down, community groups continued to press Don't Tear It Down to come up with legislation that could be enacted.

In response to the demand, David Bonderman drafted a bill based mainly on an Alexandria law that requires owners who want to demolish landmark buildins to put them up for sale at fair market value. He presented the draft to a group of community activists from Georgetown, Anacostia, LeDroit Park, Dupont Circle and Capitol Hill, and the group sent it back to the drawing board.

"It was a good meeting," recalled Smith. "They all articulated their problems. Capitol Hill wanted to control new construction (in the historic district). Anacostia needed flexibility. They wanted to encourage new construction. Georgetown was worried about subdivisions."

City officials soon got wind of the plans and offered to work with preservationists. There followed a series of meetings of a small group consisting of representatives of Don't Tear It Down and staff members of the Joint Committee on Landmarks and of the Corporation Counsel's office. By the last spring, the draft was in final form and beginning to circulate among the various D.C. government departements for comment.

Don't Tear It Down again presented the revised bill to community groups, then waited for Mayor Washington to introduce it. The mayor announced the legislation at a candidates' forum on Capitol Hill June 14, but indicated he would not rush to send it to the Council. Three days later, Council member John Wilson obtained a draft of the bill and introduced it. Nadine Wnter, who had asked Odn't Tear It Down to devise landmark legislation a year or so earlier, became a cosponsor.

In an attempt to reconcile differences expressed at public hearings in July, Winter set up an ad hoc committee, including representatives from community groups, government agencies, the American Institute of Architects and the Metropolitan Washington Board of Trade.

"It was an excellent experience," said a Board of Trade spokesman who attended many of the meetings. "We were able to sit around a table and discuss everything. From our point of view, we were able to make some improvements, to change some definitions, to mitigate some negative effects."

Specifically, the procedure for obtaining a demolition premit in order to construct a "project of special merit" was modified to the satisfaction of the Board, which dropped opposition to the bill.

When the council started debating the revised bill in October, ther were two main lines of substantive opposition. Many architects opposed the regulation of new construction in historic districts as bureaucratic interference in a creative endeavor.

Milton Shinberg, an architect who had helped work out the compromise that saved three Maryland Avenue houses, said, "Though preservation laws genuinely seek to protect us from the worst, legislative intervention into a creative process, namely architectural design, necessarily also confounds the best. It places in the hands of a committee composed of unlike minds the power to shape what has always been and what always will centrally be an individual creative process, founded on experiment and risk."

Council members Willie Hardy and William Spaulding also raised the issue of elitism, claiming that the legislation would accelerate the displacement of poor persons from inner city neighborhoods. Backers of the legislation, however, denied the charge.

"It's not elitist," said John Tetrault, an official of Neighborhood Housing Services, a group that promotes home ownership in Anacostia. "There was a conscientious effort to take into consideration the needs to take into consideration the needs of the different kinds of historic districts and to involve residents of every historic district. And there's an anti-displacement aspect to the law. There have been a number of homes torn down in Anacostia that wouldn't have been torn down under the new law."

The new law, in Bonderman's view, provides the "stick" incentive for historic preservation, but not the "carrot." What is needed now, according to Bonderman, are more financial incentives to make historic preservation attractive to property owners.

The Board of Trade, according to a spokesman, is currently working on a set of legislative proposals to provide tax incentives for historic preservation.

White, who helped put through the original delay regulation, later became assistant director of the Municipal Planning Office, and is now an attorney with a law firm that often repredents developers, also said additional incentives are needed.

"We've got to see that money flows in and buildings are restored, but the owners aren't disadvantaged," said White. The key, he suggests, is flexibility in deciding what can be built where and in allowing transfers of development rights.

"Revitailzation is occurring in the city, as on K Street," said White. "But the historic preservation people suggest that developers do something different. We have to harmonize the goals of revitalization and retention, and the tools and techniques for doing so are just beginning to be understood. We have to learn how to apply them without throwing the baby out with the bathwater."