Boston is holding a tribute event on the anniversary of the deadly bombing at last year’s marathon.
Vice-President Joe Biden told survivors they were an example of “pure courage”.
Boston’s leaders thanked those who saved lives in the frenzied aftermath.
Three people were killed and some 264 injured when two bombs exploded near the finish line at last year’s Boston Marathon.
“I know that no memorial, no words, no acts can fully provide the solace that your hearts and soul still yearn to acquire,” Joe Biden said at a midday memorial program.
“I hope it eases your grief a little bit.”
Participants in Tuesday’s ceremonies included representatives from families of the victims, members of the city’s fire, police and ambulance services, government agencies and civic organizations.
Dignitaries in attendance included Joe Biden, former Mayor Thomas Menino, current Mayor Martin Walsh, Governor Deval Patrick, Senator Elizabeth Warren, and others.
This year’s Boston Marathon is due to take place on April 21.
Tuesday’s memorial events began with a wreath-laying ceremony at the site of the explosions, attended by the families of the three bombing victims – Martin Richard, Krystle Campbell and Lu Lingzi.
Relatives of university police officer Sean Collier, who was killed during a manhunt for the suspects, also attended the solemn ceremony.
An invitation-only audience of about 2,500 people gathered at the city’s convention centre at midday to remember victims and honor those who responded to the attack.
“This day will always be hard, but this place will always be strong,” Thomas Menino said.
“Even though the memory still brings tears to our eyes and our heart aches for those we have lost, it’s a comfort to be here with family and friends who got us through that tragic day.”
Several survivors spoke at the event, including Patrick Downes and dancer Adrianne Haslet-Davis, both of whom lost their lower left legs in the bombings.
“We should have never met this way, but we are so grateful for each other,” Patrick Downes said, describing the sense of community that has developed among those who were injured.
The program finished with remarks from Joe Biden, who said last year, “the whole world witnessed ordinary people doing extraordinary things”.
The vice-president ended the tribute to loud applause: “We are Boston. We are America. We respond. We endure. We overcome, and we own the finish line.”
As the race approaches, officials have warned residents and visitors to expect a larger than normal police presence in the city streets.
However, Boston Mayor Martin Walsh said it would be “the Boston Marathon as it has always been”.
“Our goal is for everyone to enjoy the race,” he said.
City health officials say they have also made preparations to help those affected by the bombings cope with the anniversary.
Bombing suspect Dzhokhar Tsarnaev, 20, is due to stand trial in November. He has pleaded not guilty to 30 charges, of which 17 carry the possibility of capital punishment.
Prosecutors allege that Dzhokhar Tsarnaev set off two pressure cooker bombs with his older brother Tamerlan, 26, who later died in a police shoot-out.
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