In the final paces to become the first American to win the Boston Marathon in 31 years, Meb Keflezighi slapped hands with fans lining Boylston Street, where two bombs detonated during last year’s race, killing three and injuring 260.“As an athlete, you have dreams,” he said. “Today was the day when dreams and reality met. My career is fulfilled.”Keflezighi led for most of the 26.2-mile run, and even earned the cheers of his competitors as he flew past them toward the finish line. He crossed the tape after 2 hours 8 minutes 37 seconds, a personal best.“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, when American Greg Meyer won. While Keflezighi is a familiar name and successful marathoner, nothing about his life fits history or convention.Keflezighi is one of 10 children. He fled to Italy from Eritrea with his mother and his siblings while his father worked cleaning jobs to support the family and arranged for them to immigrate to San Diego. Keflezighi was a high school champion who went on to thrive at UCLA, where he won multiple NCAA championships.Keflezighi and Josphat Boit, a late entrant, pulled away from the pack midway through Monday’s race. After the runners hit the Newton hills, Keflezighi pulled away from Boit, who finished 11th.“He was so far away,” Kenyan Wilson Chebet said, “I couldn’t see Meb. I only saw straight road.”Around the 20th mile, Keflezighi said he fought off a stomach ailment and “prayed a lot” to earn the title.Rita Jeptoo of Kenya successfully defended her women’s title, pulling away in the final three miles to win Boston easily for the third time. Besides winning last year, Jeptoo, 33, also won in 2006. She set a course record of 2:18:57 on Monday, and the top four women all beat the former course record of 2:20:43.