Framed photographs of LEED-certified buildings line the hallways of the U.S. Green Building Council's new headquarters, one floor of an office building in Washington, D.C. They are family photos, in a way, and Tom Hicks, the man who runs the LEED program for the council, can't remember the names of a few of the cousins. Even the photo on the wall of his own office stumps him. “I'll get it wrong,” says Hicks, blaming unfinished decorating business. “We need to get our plaques up.”

You can hardly fault him. Some 800 buildings around the country have now received the council's stamp of environmental approval, and 6,000 more sit in LEED's pipeline. Gone are the days when every certified building was a celebrity, lavishly covered by the press and instantly recognizable. Today, the news about green buildings is that they're no longer newsworthy. Everyone from Bank of America to the U.S. military is building them—and paying the U.S. Green Building Council, or USGBC, to vouch for their bona fides.

As green goes mainstream, the council is emerging as one of architecture's new power brokers. Already, for many people, the LEED brand (the acronym stands for Leadership in Energy and Environmental Design) is tightly intertwined with the very concept of sustainable design. And it's making an impact on how the building industries work. Robert Kobet, a Pittsburgh architect who's active with the USGBC, isn't exaggerating when he says, “The LEED rating system has become the de facto green building code in this country.”

The result is that corporate and political leaders are turning more than ever to the council for guidance. That's even truer now that the debate over global warming is shifting from whether or not it's happening to the question of what to do about it. Some 53 cities, 17 states, and 11 federal agencies have put policies in place to encourage or require new government buildings to meet LEED's standards. Last December, the District of Columbia became the first jurisdiction to require LEED certification for private buildings, too—the mandate begins in 2010 and applies to structures of 50,000 or more square feet. A growing number of cities are offering tax breaks or other perks to private builders who achieve LEED certification.

Now, the USGBC is leveraging LEED to expand its reach even further. The organization has set the audacious goal of certifying 100,000 green commercial buildings by 2010. It's piloting new versions of LEED to rate the green credentials of individual homes and to assess whether entire neighborhoods truly qualify as “smart growth.” It's working on a range of other new green standards for schools, retail, health care facilities, and laboratories. And it's trying to raise the environmental performance of all buildings, LEED-certified or not, by working to green the building codes that govern construction in almost every city and state.

These are big ambitions for a nonprofit with such a diverse constituency. The USGBC's heart is a vast and sometimes disputatious membership of 8,000 design firms, developers, engineers, trade groups, and government agencies. An unpaid board of volunteer directors sets policy for the council. New ratings systems are developed by committees of volunteers, who work through a painstaking consensus process to come up with ratings systems that are put to a vote by all members.

As Hicks sees it, the USGBC's challenge is to figure out how to keep growing without watering down its famously rigorous standards. “That's paramount to our success,” Hicks says. “We don't want to have 100,000 buildings that are certified as some lower quality of LEED.”

An equally important challenge comes from critics who have long complained about LEED's bureaucracy and the costs of complying with it. In fact, several industry groups have stopped complaining and taken aim directly at the USGBC by launching their own ratings systems. The new competitors may not be able to beat LEED. But they just might undo the USGBC's lock on what “green” means.