Chicago, IL: Sears Tower Greening

At 1,450 feet and 110 stories, Chicago's Sears Tower is the tallest building in America . And soon—if officials have their way--the landmark building, all 3.8 million square feet of it, may become the largest green structure in the United States . In announcing the initiative, former president Bill Clinton stressed the benefits of green building. And they’re not only environmental. "This is not a big bottle of castor oil we have to drink," he said. "This is the greatest economic opportunity that our country has had to mobilize and democratize since we mobilized from World War II." So what will set the building apart from it’s not-so-green neighbors?

(Photo courtesy of Sears Tower)