Wanjiru won the marathon with the fastest time on American soil, finishing in 2 hours, 5 minutes, 41 seconds, and collected a big bonus check on a bone-chilling Sunday morning.
With temperatures in the low- to mid-30s, Wanjiru turned in the best time in the U.S. and beat by one second the mark set by Khalid Khannouchi in Chicago in 1999. He got $75,000 for winning and $100,000 for the course record, although he nearly cost himself that bonus by waving to the crowd as he approached the finish.
Had he finished a second later and not broken the record, he would have received an extra $75,000 instead for posting one of the three fastest finishes in the race's history.
"I was very happy to see I'm the winner," Wanjiru said. "I was very happy. I was very happy to take $100,000 by one second."
He had no idea how close he was to the course record as he headed north up Columbus Drive to the finish line, and he wouldn't have been in such a great mood had that celebration cost him. It didn't, so he could smile about it.
Abderrahim Goumri of Morocco made a late push to finish second in 2:06:04, with Kenya's Vincent Kipruto in third (2:06:08).
Russia's Liliya Shobukhova, who finished third at the London Marathon earlier this year, was a winner in her second marathon and finished all alone in 2:25:56. London winner Irina Mikitenko of Germany (2:26:31) finished second to clinch the 2008-09 World Marathon Majors championship, and defending champion Lidiya Grigoryeva of Russia was third (2:26:47).
American Deena Kastor, the Chicago winner in 2005, placed sixth (2:28:50) in her first marathon since breaking her right foot in the Beijing Olympics.
"It's very exciting," the 21-year-old Shobukhova said. "It's a great surprise for me."
Nearly 35,000 runners braved the cold and started the race, and Wanjiru and the leaders took a shot at the world record of 2:03:59 set by Haile Gebrselassie of Ethiopia at Berlin last year. They fell off during the latter stages, but the course record, remained for the taking.
After fellow Kenyan Patrick Ivuti dropped from the lead in the 16th mile, Wanjiru moved to the front and ran with countrymen Vincent Kipruto and Charles Munyeki before pulling away.
He didn't seem to be bothered too much by the cold, which was a sharp contrast from the previous two races in Chicago.
In 2007, with high humidity and temperatures soaring into the high 80s, the race was stopped after about four hours _ but not before a man with a heart disorder died. Hundreds of runners collapsed or vomited and 184 went to hospitals.
Last year, there were no major incidents, although the conditions were far from ideal. Temperatures went from 65 at the start to the high 70s while the elite runners were still on the course, before reaching 84 in late morning. Seventy-six runners had to go to hospitals.
The heat havoc came after a scary scene unfolded at the end of the 2006 race, when champion Robert Cheruiyot of Kenya slipped and banged his head as he crossed the finish line.
There were no obvious mishaps this time, Wanjiru's waving near the finish notwithstanding. It was another big win and another big day for a runner who was raised by a single mother who farmed for a living, and was discovered by a Japanese writer scouting Kenyans seven years ago.
He moved to Japan at age 15 to study and train, setting a course that has led to him becoming one of the top marathon runners, one who's eyeing the world record. Pacing himself would be a good idea.
"He can do very good things at the marathon but he should learn," Goumri said. "It's a new experience for them, the marathon. You should have two, three years (running) marathons. Then you can do the world record."
On the women's side, it was an emotional day for Mikitenko.
The two-time London Marathon champion pulled out of the world championship in Germany in August after her father died. With her mother celebrating a birthday Sunday, she turned in a solid performance that came up just short of Shobukhova.
So did Kastor, who is trying to re-establish herself at 36 and set a course toward the 2012 London Olympics _ something she might not be doing had things gone better in Beijing.
"I feel really good about where I am right now," said Kastor, the bronze medalist at the 2004 Athens Games. "My day fell a little short, but I'm still pretty ecstatic by how my body has held up and how strong I've gotten over the past few months."