The late Constance Prosser Mellon rode horses nearly every day and frequently led camping trips to Alaska, where the family matriarch once pulled a guide's bad tooth without any medical assistance. Her sons Richard and Prosser kept raccoons, deer, a fox and skunk as pets while they were children in the 1950s.

	Map: Mellon conservation projects, coast to coast

"We grew up with the outdoors at the center of our lives," Richard Mellon once said.

Fitting, then, that the Mellon family would quietly launch a land preservation conservation campaign in the late 1970s that now stands as one of the great achievements of the modern American conservation movement: 3.6 million acres of endangered or historically significant sites saved across the country, in all 50 states -- farms and forest and waterfalls and prairies and desert lowlands and meadows and lakes and streams, from the rocky, sea-splattered coast of Maine to the north rim of the Grand Canyon to Hawaiian rain forests.

The amount of money the Mellons spent to save all that land from suburban sprawl or second-home expansion stands at $503 million, all of it funneled through the Richard King Mellon Foundation, with assets of $1.9 billion. It's Pittsburgh's largest philanthropic group and one of the 25 largest in the country.

The family attracted financial partners to help with many of the purchases and donated all the land to federal and state agencies and nonprofit wildlife groups. (Even 19,000 acres in southwest Georgia still owned strictly by family members is used primarily for farming, fishing and quail hunting.)

"I think it will go down in history as the largest private land conservation effort ever," said Larry Selzer, president of The Conservation Fund, an Arlington, Va.-based nonprofit that works with the Mellons on many of their purchases, often acting as a front group to discourage greedy sellers.

Their "contributions to land conservation," said The Heinz Endowments President Max King, "are nothing short of heroic."

No other private group has purchased -- and protected -- so much land so quietly. The only other American family to rival the Mellons in this category is the Rockefellers, who are responsible for the land purchases behind more than 20 national parks, including Grand Teton in Wyoming and Acadia in Maine.

The largest individual land owner in the United States is billionaire cable pioneer Ted Turner, but even his holdings of 2 million acres do not approach the Mellons' total collection over three decades. Much of Mr. Turner's land is in the Southwest, where he raises bison, allows some timber harvesting, hunting and fishing. Mr. Turner's son in law, J. Rutherford Seydel II, is on The Conservation Fund's board as vice chairman, and Mr. Selzer of The Conservation Find admits that there have been "discussions" about the future of that Turner land.

For the Mellons, the irony of their land campaign is the family's history as financier to the oil, aluminum and steel industries -- all gritty pursuits. Richard King Mellon, who ran the family's banking interests through the middle part of the 20th century, spent decades after World War II on efforts to clean Pittsburgh's rivers, its skies and improve the appearance of its tattered urban landscape -- a public-private campaign that became known locally as "the Renaissance."

He created the Richard King Mellon Foundation in 1947, and his wife Constance, the woman who pulled that tooth while hiking through Alaska, chaired the group from its founding until her death in 1980. While the foundation made its first land purchase in 1972 -- $150,000 toward a $1.4 million acquisition of a Charleston, S.C. blackwater swamp -- the foundation's priorities shifted most significantly in 1976, when it inaugurated an acquisition program "to secure and protect America's significant natural land areas for future generations."

Breaking new ground
"This was an area where they could carve new ground," said Michael Watson, the foundation's senior vice president. "There wasn't an awful lot being done by philanthropies for conservation. This was an area where we could take a lead."

The family spent $73 million between 1972 and 1987 protecting 1 million acres, including several hundred thousand acres of hardwood forest alongside six rivers in the Deep South. But the campaign really picked up in the years between 1988 and 2002, when Richard and Prosser as chairman and president of the foundation spent $400 million on 190 properties, reaching a goal of acquiring sensitive land in all 50 states.

They snapped up the former Wyoming vacation retreat of Amelia Earhart; a New Mexico "Forked Lightning" ranch featuring Spanish ruins and wagon-wheel ruts left from the Santa Fe Trail; a path worn by American explorers Lewis and Clark; and key Civil War battlefield sites, including a cornfield in Antietam where someone wanted to build a bed-and-breakfast on the site where 23,000 Americans died during a single day of fighting in 1862.

In several cases, the Mellons swept up the land before a developer could proceed with resorts or condos. With one, it had to outbid a Japanese company in bankruptcy court for 150 square miles of wetlands along North Carolina's Alligator River -- the Japanese wanted to eliminate the wetlands and mine the peat for power production. The price was $9 million.

During that period, the Mellons would sometimes allocate half of their yearly grant-making to environmental causes. One of the largest single allocations was the $35 million spent protecting a small strip of beachfront in Melbourne, Fla., where turtles nest. The site has been threatened by residential and commercial development.

In 2003, the Mellons promised to wind back their national purchases and concentrate more on lands in Western Pennsylvania, hoping others would take up their cause around the country.

But in 2005, they paid half of the $5 million needed to purchase the grazing rights for nearly 900,000 acres along 80 miles of the Grand Canyon's North Rim -- a fly zone for the endangered California condor. Among the partners were Wal-Mart, the world's largest retailer, and the Grand Canyon Trust. The goal was to prevent overgrazing and manage the land so that it preserves all sorts of species beyond cattle. It was the largest single private conservation purchase in the history of the country, according to The Conservation Fund.

"A massive piece of land," said foundation director Scott Izzo.

Last year, the Mellons also contributed $1.59 million toward the purchase and protection of a northern Maine fishing and hunting haven known as Grand Lakes Stream. The foundation purchased the development rights for 312,000 acres owned by a timber company, ensuring that land along the lakes of the area would not be turned into oversized vacation homes.

This year, in New York state, the Mellons pledged another $4.38 million toward a $35 million purchase of development rights to timber land in the Adirondacks. The land still will be timbered but the purchase means the lakelands will not be "flooded with cabins and trailers and things like that," said Mr. Watson, the foundation's senior vice president. It is the largest such deal in the history of New York state.

Focusing close to home
Still, there is evidence that the Mellons, many of whom live in Ligonier, are focusing more and more on the area they still call home (the family members themselves own about 8,000 acres in Ligonier known as Rolling Rock Farms).

For example, the foundation recently spent $3.5 million on the acquisition and preservation of 4,000 acres in Cambria County and $2.2 million on 724 acres in Somerset County where the Pittsburgh Zoo will breed elephants in the not-so-distant future. With help from The Conservation Fund, the foundation is also trying to acquire about 2,000 acres surrounding the hallowed Flight 93 crash site near Shanksville, Somerset County. Currently about 200 acres are under control and Mr. Selzer of The Conservation Fund said talks are under way with the owner of the rest -- PBS Coal.

Foundation officials say a new generation of Mellons -- six grandchildren of Richard King Mellon recently joined the board -- have the same appreciation for land and wildlife as their parents and they expect no changes in focus as older members Richard and Prosser, both in their 60s and avid hunters of upland birds, enter retirement age.

But the Mellons want other foundations around the country to get involved, as well, and admit that conservation is not always a high priority in the philanthropic world -- even as about 3 million acres of land per year are lost to sprawl, according to The Conservation Fund.

"The lands that have defined us as a people and shaped us as a nation, the American landscape, is changing right before our eyes," said Mr. Selzer. "We are in danger of losing that very legacy that ... what the Mellon foundation has done is step into the breach."

And the Mellons did it quietly, said Jay Espy, president of the Maine Coast Heritage Trust. Decades after it began, though, the campaign has ensured the family a reputation as "one of the giants, if not the giant, in the land conservation world."