A citywide moment of silence was observed and the bells of the Old South Church were rung to mark the exact time the first bomb exploded.
Earlier in the afternoon, Massachusetts Gov. Charlie Baker and Boston Mayor Marty Walsh joined the families of the bombing victims in laying ceremonial wreaths near the marathon finish line.
In 2013, two bomb blasts went off near the finish line of the Boston Marathon on Marathon Monday, which fell on April 15 that year.
In addition, the two men identified as the bombers shot and killed MIT police officer Sean Collier days afterward.
The attacks created an outpouring of local support and resilience that came to be known under the hashtag #BostonStrong.
Two years after the attacks, the city of Boston officially named April 15 One Boston Day, marking it as a day to encourage acts of kindness and goodwill.
“Perhaps we rely on the notion that we need life-altering situations to make kindness matter. Kindness need not be displayed in random acts but with intent and purpose. Kindness is a vital part of the effort to foster a peaceful and just region, nation and global community.
“Kindness supports human dignity and should be shared freely, neighbor to neighbor, block by block until everyone is recognized as equal,” he said.
Baker, the Boston Police Department and Rep. Joseph Kennedy III were among the politicians and organizations that posted remembrances in honor of the victims.
CNN’s Amanda Jackson contributed to this report.