One of the nation's leading historical preservation organizations announced a campaign yesterday to provide financial and technical support to more than two dozen southern black churches that have been hit in the recent rash of arson fires.

The Washington-based National Trust for Historic Preservation said in announcing its annual list of the 11 "most endangered" historic places that it would make the churches its 12th selection.

"We are taking this unprecedented step because of the urgency to mobilize support for some of the most significant community institutions in America," said National Trust President Richard Moe, who pledged an undetermined amount in loans and other aid to communities with black churches that have been damaged.

Intentionally set fires have destroyed about 30 black churches across the South in the last 18 months. Three federal agencies are investigating them, and President Clinton has denounced the fires. A black church in southeastern North Carolina was destroyed early yesterday, but authorities did not know whether that fire was arson.

Other organizations are joining the cause. NationsBank was one of the first to put up $500,000 for information leading to the arrest and conviction of people responsible for the attacks.

The National Trust's list of endangered historic places is intended to alert communities to threats from demolition, neglect, lack of funding and sprawl-type development -- "but never, until now, the danger of arson," Moe said. The 250,000-member group is perhaps best known in this area for helping to force the Walt Disney Co. to scrap its plan for a theme park in western Prince William County.

Also on the trust's list is the Sotterley Plantation, a circa 1710 plantation near Hollywood, Md., in St. Mary's County. Descendants of a slave and a slave owner are trying to keep the remaining buildings of the plantation open to the public. But the buildings are deteriorating.

Central High School in Little Rock, which got national attention when it was integrated in 1957, also was on the list. It suffers from structural damage.

The list, which changes every year with limited success stories, also contains the Knight water-powered foundry in Sutter Creek, Calif.; adobe churches of New Mexico; the historic structures of Glacier National Park, in Montana; the 71-year-old Uptown Theatre in Chicago; the Harry S. Truman historic district in Independence, Mo.; the East End historic district of Newburgh, N.Y.; Wentworth by the Sea hotel in New Castle, N.H.; the East Broad Top Railroad in Huntingdon County, Pa.; and the town of Petoskey, Mich., which is threatened by sprawling development.