About 2,500 invited guests attended the memorial at Boston's Hynes Convention Center, just blocks from the race's finish line where a pair of homemade pressure-cooker bombs detonated a year ago, ripping through the crowd of spectators.
"You have struggled to get through the good days and the bad," said former mayor Thomas Menino, who stepped down at the end of last year after his sixth term in office. "I know because so many of you have told me about this year of firsts. First birthday without your beloved son, first holiday without your daughter, first July 4 where the fireworks scared you."
Menino, who had been hospitalised at the time of the blasts but responded to the scene against his doctor's orders, praised Boston residents' response.
"You are strong at this broken place," said Menino. "That strength thrives even in the heartaches of today because of the compassion that took over this city."
The April 15, 2013, attacks, which federal prosecutors have blamed on a pair of ethnic Chechen brothers, killed Martin Richard, 8, Krystle Campbell, 29, and Chinese national Lu Lingzi, 23. It was the worst mass-casualty attack on US soil since the September 11, 2011, attacks that killed some 3,000 people.
Three days after the bombings, a Massachusetts Institute of Technology police officer, Sean Collier, 27, was shot dead by the same brothers, prosecutors said.