When summer visitors come to the viewing platform to see Snoqualmie Falls, one of Washington's main tourist attractions, few of them realize they are also looking at an example of a unique and successful land management and planning exercise.

The falls are backed by more than 100 acres of lush and unscarred green forest, once destined for commercial and housing development by Puget Western Inc. and the city of Snoqualmie. But the Cascade Land Conservancy, a private nonprofit, stepped in and bought the property for $13.3 million.

It was something of a gamble, said the conservancy president's, Gene Duvernoy, because the sum was twice the net worth of his organization. "We were a little over our skis," he said. But having nursed the organization through its first four years from its start in 1989, working out of the attic of his house, the former New Yorker was accustomed to improvising.

His strategy was to "solve the problem by enlarging it." He first approached Weyerhaeuser Co., which had recently built 3,000 homes on a nearby tract but had agreed with the city, as a condition for that construction, to defer building Phase 2 of the project, where sewer lines had already been installed, for 20 years.

Duvernoy struck a deal. The conservancy went to the city fathers and persuaded them to let Weyerhaeuser build Phase 2 now, rather than wait 20 years, in return for the company's financing 90 percent of the purchase price of the tract behind the falls. He then went to King County officials and got them to transfer development rights on 3,000 acres of land along Highway 18 that the county wanted to protect to the Phase 2 land, allowing more density of housing. The county in turn transferred the 3,000 acres to the conservancy for safekeeping.

When Duvernoy walked me through the transaction on a recent visit to the falls, he called it a "win-win-win-win deal" for the city, the county, the company and his own organization. It reflected "the unbridled strain of civic commitment in our region, with progressive business leaders, talented elected leadership and engaged citizens," he said.

Now the conservancy is testing that commitment with an enormously ambitious plan, made public last month, called the Cascade Agenda. The plan, looking ahead to a century of growth expected to double the population in a four-county region, aims to make almost 1.3 million acres of forests, farms and stream beds in the Cascades foothills -- an area 24 times the size of Seattle -- permanently off limits to developers. And it aims to foster the healthy growth of the cities and towns within the region.

The agenda, hammered out in a year-long series of community forums, relies less on regulation than on market-based tools, notably swaps of development rights of the kind exemplified by the Snoqualmie transactions.

The project is expensive -- about $7 billion in current dollars -- because it requires compensating landowners who give up development rights on their property. But the creators of the blueprint say it can be financed in phases by boosting the annual local and state government expenditures for conservation, now estimated at $50 million a year, to $70 million.

Because the acquisition of development rights would ideally come in the early stages of the process, the conservancy is backing legislation in Congress that would allow groups like itself to issue tax-exempt bonds. Bills for that purpose have passed both the House and Senate, but never reached the president's desk.

While the emphasis is on preserving the natural environment that accounts for the region's appeal, and the farms and orchards that were there long before such industries as Boeing Co. and Microsoft Corp. appeared on the scene, the agenda recognizes its essential urban component.

"We can only succeed at this conservation vision if our cities and towns really become magnets for our region's future population growth," Duvernoy wrote in a recent newspaper op-ed. "If cities and towns truly become family-friendly, with good roads and schools and nearby jobs so that we want to live within them and not outside them, the pressure on our critical landscapes will be at a level our market-based strategies can manage."

The scale and ambition of this project make it nationally significant. That it has even the possibility of success speaks volumes about the character of this region and its leadership.