What isn't clear is how much time Canada has. Donors may grow fatigued. Canada may lose the spotlight and his "It Guy" status as an expert consulted by youth agencies from as far away as India. More immediately, he may not meet a key 2007 milestone--adding an extra 31 blocks to the 60-block Zone, which began in 2001 with 24. Marian Wright Edelman, president of the Children's Defense Fund, concedes these are stingy times for public funding. But, she says, "if anyone can do it, it's Geoff Canada."

Canada grew up in the South Bronx. His father left the family when Canada was 4, and his mother raised him and three other sons alone, working at menial jobs and sometimes taking welfare. In his memoir, Fist Stick Knife Gun, he says that he drank as a teenager and got into street fights. But he stayed in school and earned a scholarship to Bowdoin College.

One of Canada's favorite measures of the Zone's success is a map covered with stickers showing where 110 Zone alums last year attended college. In his own office are personal photos--and a few ghosts. Absent from one group photo are about a half-dozen siblings and friends killed by inner-city violence. The family photos are missing one of Canada's older brothers, John, who died at age 22 after a freak basketball injury.

When Canada, a third-degree black belt who still teaches tae kwon do, joined the Zone's predecessor agency, Rheedlen Centers for Children and Families, in 1983, his focus was more on saving lives. He ran after-school antitruancy and antiviolence programs. After he took over Rheedlen in 1990, the $2.5 million program, which was serving 1,500 children, grew and diversified. But Canada was still impatient.

Waiting lists at Rheedlen frustrated him, making him feel that they were saving just the lucky few. A presentation from now Savannah, Ga., Mayor Otis Johnson on holistic services for poor children in specific geographic areas inspired him. The Edna McConnell Clark Foundation offered Canada $240,000 to design a new program--and millions more if milestones were met. When Canada held a retreat and asked middle managers to "dream the perfect Harlem," the ideas flowed.

But the single most influential factor was, Canada says, "Stan." Stanley Druckenmiller, a fellow Bowdoin alum, billionaire hedge-fund manager, and poker player, was on Rheedlen's board of trustees when Canada proposed the Zone. "I was struck by its boldness," Druckenmiller says. "And, frankly, from anybody else I would have dismissed it as too utopian and unattainable. But watching Geoff over the years, I thought it was crazy not to take a shot with this guy."

In 1998, the two decided they couldn't meet fundraising goals with the existing board. So Canada says he did one of the toughest things he's ever had to do. "I had to tell people they'd gotten us to a level where we didn't need them anymore," he says. Druckenmiller became chairman and brought in more Wall Street high rollers who contributed significantly to a new building and to the Zone's current $36.3 million annual budget. About 70 percent comes from donors and foundations, 30 percent from government.