Lee Ann Yanni, whose left leg was badly injured in the bombing, said she could feel the energy of the crowd pushing her to the finish.
"It was really emotional crossing the finish line," she said. "We got our finish line back. That's all that mattered."
The elite racers gave the crowd a reason to cheer, too.
American Meb Keflizighi won the men's title in 2 hours, 8 minutes, 37 seconds, the first American man to break the tape since 1983. Keflizighi had the names of last year's victims written in black marker on the corners of his race bib.
Kenya's Rita Jeptoo won the women's race in a course-record 2 hours, 18 minutes, 57 seconds, defending a championship from last year. She had been hoping this year for a title she could enjoy.
"It was very difficult to be happy. People were injured and children died," she had said of last year's marathon.
There was no denying the security measures in place since last year: There were multiple checkpoints; police along the route examined backpacks, particularly outside subway station exits; more than 100 new surveillance cameras looked down from above; and runners carried their belongings in clear plastic bags.
At 2:49 p.m., the moment the bombs went off a year ago, there was a moment of silence followed by a swelling cheer that chased runners toward the finish, rising in a wave as it got closer to the blue and gold line that marks the end of the race.
Vicki Schmidt of Nashville, heard the explosions last year while running on Commonwealth Avenue, but thought they were fireworks. She was prevented from finishing the race and her boyfriend, Phil Kirkpatrick, suffered hearing loss from the bombings. This year, he walked and ran the course.