American Meb Keflezighi won the Boston Marathon men's title on a day that was marked by remembrances of the bombings one year ago.
He held off Wilson Chebet at the finish to win in an unofficial time of 2:08.36.
Keflezighi, who will turn 39 next month, was cheered by massive crowds from Hopkinton to Boylston Street wearing a red and white top and blue shorts. He's the first American man to win in Boston since Greg A. Meyer in 2:09:00 in 1983, four years before Keflezighi immigrated to the U.S.
The 2004 Olympic silver medalist was born in Eritrea and lives in Mammoth Lakes, Calif. His last major marathon victory was the Olympic trials marathon in 2012. He won New York in 2009.
Keflezighi broke away from Josphat Boit, an American runner who was born in Kenya, midway through the race. By mile 17, Keflezighi had a minute lead over the pack that included defending champion Lelisa Desisa of Ethiopia.
The American's victory came somewhat of a surprise on Patriots' Day. A runner from Kenya or Ethiopia has won the last 12 men's titles in Boston.
Rita Jeptoo of Kenya defended her title in the women's race. American Shalane Flanagan set a fast pace through the first half, leading the women's pack at the halfway mark.
Jeptoo defended the title she said she could not enjoy a year ago after the fatal bombings.
Jeptoo finished Monday's race in a course-record 2 hours, 18 minutes, 57 seconds. She becomes the seventh three-time Boston Marathon champion.
A year after a pair of homemade pressure-cooker bombs killed three people and wounded more than 260 others at the Boston Marathon, runners and spectators filtered in Monday morning at the starting line in Hopkinton amid tight security.
About 36,000 runners had registered for the race - the second-largest field in its history, many of them coming to show support for the event and the city that was shocked by the attack on its signature sporting event.
"I can't imagine the number of emotions that are going to be there," said Katie O'Donnell, who was running the marathon last year and made it 25½ miles before she was stopped less than a mile from the finish line when the twin bombs exploded. "I think I'm going to start crying at the starting line and I'm not sure I'll stop until I cross the finish line."
The most obvious change for the 118th edition of the world's oldest annual marathon was the heavy security presence. State and local police officers were everywhere, even on the rooftops of some buildings.
But rather than creating a tense situation, everyone appeared relaxed. Some runners even thanked the police officers for making them feel safe.