Boston - Something unusual happened when Meb Keflezighi, far ahead of his competitors, began passing some of the elite women who had started before the men in Monday's Boston Marathon. As he charged by, many of the women - exhausted and in pain - cheered him on.

Keflezighi will turn 39 in two weeks, an age when most elite marathoners have lowered their expectations to respectable rather than victorious. So many years of competition over 26.2 miles tends to pull the swiftest back toward the pack with tendinitis here and a fractured bone there. Keflezighi, however, seems to be getting younger, defying all that is understood about the sport in a most spectacular way and winning the enthusiastic support of many runners in the field.

On Monday, in a race that had taken on greater meaning because of the act of terrorism it was witness to a year ago, Keflezighi became the first American man to win the Boston Marathon in more than 30 years, and he did it in a personal-best time of 2 hours, 8 minutes, 37 seconds. He is the oldest Boston Marathon winner since at least 1930, when 41-year-old Clarence DeMar won for the seventh and last time.

The race, the world's oldest annually run marathon, felt like a catharsis for this city. A crowd of 1 million people, twice the usual number, showed up to cheer the runners, which featured 36,000 athletes, 9,000 more than usual. Twice as many law enforcement officials patrolled the race course as well.

Keflezighi gave fist bumps to the enormous crowds on Boylston Street, near where two bombs went off at the 2013 marathon, killing three and wounding more than 260. Once across the finish line, he was hugged by 1983 champion Greg Meyer, the last American man to win the race. Keflezighi then bowed to the crowd and waved to the spectators in the grandstand at the finish line.

"This is probably the most meaningful victory for an American because of what happened last year," he said. "I'm almost 39. I just ran a personal best. I just won the Boston Marathon. I feel blessed."

The list of winners of all major marathons in recent decades is dominated by Kenyans and Ethiopians. Runners from those countries have won 24 of the 30 Boston Marathons since 1983. Nothing about Keflezighi's story fits history or convention.

One of 10 children, Keflezighi (pronounced ka-FLEZ-ghee) fled to Italy from Eritrea with his mother and his siblings while his father worked cleaning jobs to support the family while arranging for them to immigrate to San Diego. In the seventh grade he ran a 5:10 mile. (On Monday, he sustained a pace of 4:54 over 26.2 miles.) He was a high school champion who went on to thrive at UCLA and then win a silver medal at the 2004 Athens Olympics.

At 34, Keflezighi won the 2009 New York City Marathon - the first American winner in that race since 1982. Keflezighi then won the U.S. Olympic trials for a berth in the 2012 London Games.

"My career is fulfilled," he said. "Since 2008 it's been frosting on the cake. It's just getting better and better."

On Monday, a moment of silence was held at 8:45 a.m. to honor last year's victims.

Keflezighi and Josphat Boit pulled away from the pack midway through the race. Once the runners hit the Newton hills, Keflezighi made his pivotal move. "He was so far away," said Wilson Chebet of Kenya, who finished second. "I couldn't see Meb. I only saw straight road."

Keflezighi said he fought off a stomach ailment around the 20th mile and then "prayed a lot" to make it to the finish line ahead of the fast-closing Kenyans.

Chebet finished in in 2:08:48. The defending champion, Lelisa Desisa, who is 15 years younger than Keflezighi, dropped out near the 22-mile mark, race official said.

Rita Jeptoo of Kenya defended her women's title, pulling away in the final 3 miles to easily win Boston for the third time. Jeptoo, 33, set a course record of 2:18:57. The runner-up, Buzunesh Deba of Ethiopia, also beat the former course record of 2:20:43, as did third-place finisher Mare Dibaba of Ethiopia and fourth-place finisher Jemima Jelagat Sumgong of Kenya.

Hopes for the first American women's winner since 1985 ended when Shalane Flanagan, who led a blistering pace and topped the field through 15 miles, faded on the hills of Newton.

Flanagan, who finished fourth last year, beat her personal best by three minutes and placed seventh in 2:22:02.