This year's starting field of 32,408 included 600 people who were given special invitations for those who were "profoundly impacted" by the attacks, and almost 5,000 runners who were stopped on the course last year when the bombs went off.
"Today, when I got to that point, I said, 'I have to do some unfinished business,'" said runner Vicki Schmidt, 52, of Nashville. She added: "You can't hold us back. You can't get us down. Boston is magical. This is our place."
Some of the victims themselves returned for a ceremonial crossing of the finish line.
"It was hard. It was really hard," said Heather Abbott, who wore a "Boston Strong" sticker on the black prosthesis where her left leg used to be. "I was really nervous. I didn't want to fall. ... I'm just glad we made it."
Tatyana McFadden, who was 6 and sickly when she was adopted out of a Russian orphanage by an American, won the women's wheelchair race for the second straight year. Afterward, she spoke of Martin Richard, the 8-year-old boy who was the youngest of those killed in the explosions.
"I have a Russian heritage, but I am an American," McFadden said. "For today, not only was I running for Martin and his family, but all those other people that were affected by last year."
Dzhokhar Tsarnaev, 20, is awaiting trial in the attack and could get the death penalty. Prosecutors said he and his older brother — ethnic Chechens who came to the U.S. from Russia more than a decade ago — carried out the attack in retaliation for U.S. wars in Muslim lands.
Tamerlan Tsarnaev, 26, died in a shootout with police days after the bombings.
"It was a hard last year," Lee Ann Yanni, whose left leg was badly hurt in the bombing, said moments after crossing the finish line. "And we're just so much better and stronger."
Associated Press Writers Rik Stevens, Philip Marcelo, Michelle R. Smith, Bob Salsberg, Denise Lavoie, Steve Peoples, Paige Sutherland, Steve LeBlanc and Bill Kole; freelancers Ken Powtak and Amy Crawford, and AP Sports Writers Howard Ulman and Pat Eaton-Robb contributed to this story.