A historic preservationist is a ''revolutionary'' who would rather save ''a trashy, abandoned building'' than replace it with ''a sleek new skyscraper or a much-needed parking lot,'' says David S. Gillespie, New England regional director of the National Trust for Historic Preservation.
Today's preservationists ''demand that quaint, even unused, sites and structures of historic and artistic value'' be saved, restored, or recycled, says Mr. Gillespie.
But preservationists insist they are not unreasonable or unrealistic obstructionists. They see themselves as nurturing and protecting the best from the past to provide a better perspective on the future.
Most preservationists are not antidevelopment, but they want to keep the construction of new hotels, apartment and office buildings, and industrial structures from destroying the landmarks of the past, the features that give historic cities like Boston their special character.
Gillespie says that ''quality development'' in many communities in harmony with historic preservation has been made possible by the founding of the National Trust for Historic Preservation in 1949, the designation of the National Park Service as a trustee for historic sites in 1973, and the growth of state and local volunteer preservation groups and official state and local commissions in the past 10 years.
The conflict - business and tax revenue vs. preservation and aesthetics - becomes a public issue in cities like Boston when prime real estate, although abandoned and neglected, is involved, says Marcia Myers, executive director of the Boston Landmarks Commission.
''It's especially difficult to save a building when a business wants to modernize and replace the old with what it calls a more practical and greater revenue-producing plant,'' she says.
A site or structure is not officially labeled by the Landmarks Commission until there have been extensive public hearings, which often feature quite heated debates between developers and preservationists.
Also, both the city council and the mayor must give their approval before any site becomes a landmark. Once the designation is made, the commission monitors any change that affects a landmark, directly or indirectly.
The public favors preservation, says Gillespie, citing recent examples: the saving of the Old Middlesex County Courthouse in Cambridge, which faced razing to make way for a parking lot; restoration of a monument to free blacks who volunteered to fight for the Union in the Civil War, and the huge turnout for a ''birthday party'' in honor of Boston's Faneuil Hall Complex (the historic hall, Quincy Market, and two office/commercial buildings).
The Middlesex Courthouse, an 1814 Charles Bulfinch architectural gem (enlarged a half-century later by Ammi B. Young, architect of the unique US Customhouse in Boston), was salvaged when public officials, preservationists, and fine arts patrons joined forces. Now it is being renovated under the guidance of Cambridge architect Graham Gund.
Vacated 10 years ago when an 11-story replacement was opened across the street, the deserted courthouse will reopen by the end of the year with an office complex, a new restaurant, and a center for the arts that will include headquarters for the Cambridge Multicultural Art Center (CMAC), an experimental theater, and an art gallery.
Although the exterior retains Bulfinch trademarks - golden dome and cupola with octagonal turret with round-headed turrets, four windows topped by clocks, and a minidome and steeple - Susan Harris of Graham Gunn Associates says, ''The interior is more creatively distinctive. We are anxious for people to see the splendor of the interior.''
The parking lot issue is settled, too. The architectural firm has negotiated with Middlesex County to construct a new garage financed with state funds.
Preservationists revere old Boston, the feisty relic of colonial America, and that is what most visitors want to see. Their Boston is a quaint city of low-rise, red brick buildings on narrow streets, with skyscrapers blended into the aging facade.
It's an image captured by baker George Montilio in a 5,000-pound cake, a replica of the Hub and its 19 neighborhoods, served to 20,000 participants in a public celebration of the 158th year of the opening (Aug. 26, 1826) of the original Faneuil Hall Marketplace.
Their Boston is also a massive plaque dedicated to free blacks who volunteered to serve in the Massachusetts 54th Regiment under Col. Robert Gould Shaw. It stands at the entrance to the Boston Common across the street from the gold-domed state capitol designed by Bulfinch.
Blacks from the inner city mingled with historians and philanthropists from Beacon Hill at the city's Parkman House to rejoice over the restoration.
The Park Service and the city will jointly care for the monument, and supporters have raised $200,000 to help maintain the shrine.
Various ''friends'' groups have set up endowment funds to finance the upkeep of local historic areas, and more than 50 business and civic organizations have signed contracts to maintain individual monuments and small city parks, says Robert McCoy, Boston commissioner of parks and recreation.
Probably the nation's most influential agency in the current trend to save historic sites is the National Park Service. Typical national parks in the Northeast are not in the tradition of Yosemite and Yellowstone, says Edie Shaen-Hammond, regional public-relations officer.
''Our region has only a few natural parks, Acadia, Cape Cod, Fire Island, and Gateway,'' she explains. ''We are more likely to operate in urban America.''
One urban historic national park is the whole city of Lowell, Mass. - once labeled the home of the Industrial Revolution, now a city designed to attract tourists, a city of recycled factories and row houses, a city wooing new industries, Mrs. Shaen-Hammond explains.
New England abounds in buildings that have outlived their original purposes - government structures, schools, factories, commercial, and residential areas. The region has five state preservation commissions (Rhode Island has none) as well as more than 100 local commissions.