The 175-mile road trip between Gettysburg and Monticello is a sometimes traffic-clogged passage past flag-waving outlet malls and fast-emerging suburban outposts built to serve the Washington region's booming population.

But a journey through the lands near Route 15 also takes in six presidential homes, including James Madison's Montpelier, a concentration of Civil War battlefields from Antietam to Manassas, a million acres on the national historic register and the rolling Piedmont scenery that inspired the Founding Fathers.

Yesterday, Richard Moe, president of the National Trust for Historic Preservation, put the vast tri-state area on his group's annual list of the nation's most endangered historic places. Also among the 11 sites are a Frank Lloyd Wright house in Los Angeles, historic Catholic churches in Boston and decaying buildings in downtown Detroit.

Moe and other promoters of an area they call the "Journey Through Hallowed Ground" corridor said they are seeking to boost the profile of a diverse and threatened area near the nation's capital. They argue that the corridor has lost more than 150,000 acres of farmland since the early 1980s as population there has doubled.

"I think there is more significant history in this corridor than in any comparable space in America," Moe said. "There's been a lot of encroachment already, particularly in the form of residential development. If this continues, the character of this region will be changed forever."

Some in the development community expressed skepticism at the scope of the declaration by trust officials.

"Without sounding unsympathetic to their cause, I just can't imagine you can say something from Gettysburg to Charlottesville, that entire region, is one of the most endangered areas," said Joe Paciulli, whose land surveying and engineering firm, Paciulli, Simmons & Associates Ltd., is involved with many projects in Loudoun County. He added that the development community would be interested in working on regional planning and on identifying particular areas to preserve.

"I understand historic sites, and I understand natural beauty and all those things, but when you are dealing basically just with endless fields and endless terrain, it's hard for me to relate to a statement like that. It sounds rather extreme," he said.

Just what impact the "endangered" status might have is unclear. Yesterday's announcement by the national trust was part of an effort by a broad range of groups to call attention to what they argued is widespread, often careless encroachment on an under-appreciated historic area.

A coalition of more than 100 conservation and other groups, also calling itself the Journey Through Hallowed Ground, is pushing a series of ideas to protect the area. Measures include seeking a designation from the Federal Highway Administration naming parts of Routes 15 and 20 as a National Scenic Byway, developing a teaching curriculum about the area at a local community college and promoting "heritage tourism" focused on the area's many historic homes and other sites.

The coalition also is studying the creation of a "socially responsible" investment fund to purchase land it views as threatened.

In a reflection of the proponents' efforts to find support among private donors and the development industry, organizers appointed a former developer to be the group's executive director.

Cate Magennis Wyatt of Waterford, Va., left her job in real estate development to become Virginia's secretary of commerce and trade in the administration of Gov. L. Douglas Wilder (D). She said the primary danger to the region's historic resources is "unmindfulness," saying nobody actively seeks to desecrate American heritage sites. She said that she hopes to build a public-private effort that will prove that heritage tourism can make money and that she is seeking the resources to buy endangered land to protect it.

"We fully recognize that landowners have rights to sell their land, and we are earnestly trying to find a means to purchase land at market rates," she said.

It was not the first time Moe's group has taken on such a broad "endangered" place, though it is rare.

More than a decade ago, it put the state of Vermont on the list because it saw a threat in Wal-Mart's plans. Last year, it relisted the state, again in reaction to the biggest U.S. retailer. The group also put the Colorado plateau, which covers parts of four states, on the list several years ago because of looting and vandalism of archaeological sites. This year's list also includes millions of acres of public land in 12 states overseen by the Bureau of Land Management.

"It may be a reach for some people to see the connectedness here between Gettysburg and Monticello on the other end. But the fact of the matter is this corridor is chockablock with really historic places and resources," Moe said.

"This is where the Civil War was fought. This is where our Founding Fathers lived. It just reeks of history. There are African American sites. There are Native American sites. Our whole nation's history is, in one way or another, encapsulated in this corridor."

Montpelier, President James Madison's ancestral estate near Orange, Va., is one of six presidential homes in the corridor listed as endangered.A statue of Col. James Hawley of the 124th Pennsylvania Volunteer Infantry stands at Antietam National Battlefield.