At least 35,660 runners competed in the Boston marathon, as officials stepped up security after the deadly bomb attack during last year's event.
On Monday, more than 3,500 police and members of 60 different local, state and federal security agencies deployed to protect the race.
One million people were expected to show their support for the event and honour the victims and survivors of the attacks that killed three people and wounded more than 260 last year.
Meb Keflezighi, a US citizen, won the 42km race. He is the first US winner since Lisa Larsen-Weidenbach took the women's title in 1985. The last American man to win was Greg Meyer in 1983.
Ernst van Dyk of South Africa won the men's wheelchair division for a record 10th time and Tatyana McFadden of the US won the women's race for a second straight year.
The Boston Marathon is one of the six biggest foot races in the world and part of the prestigious World Marathon Majors circuit. It is also the world's oldest annual meet.