Mayor Marty Walsh and Massachusetts Governor Charlie Baker joined with families for a wreath laying ceremony on Boylston Street in Boston, near the marathon finish line. There will also be a moment of silence across the city at 2:49 p.m., the time when the first bomb was detonated.
"Just as the world has repeatedly demonstrated after the horrors of San Bernardino, Paris, Brussels, and elsewhere, the people of Boston showed that bombs and bullets cannot break our spirit -- that freedom will ultimately overcome fear," Lisa O. Monaco, Assistant to the President for Homeland Security and Counterterrorism, said in a statement. "As we relentlessly pursue these terrorists and counter their destructive ideology, we continue to draw inspiration from a city that has shown the true meaning of Boston Strong."
Rebekah Gregory, a victim who lost her leg in the bombings, wrote a thoughtful note on Facebook, describing how her life has changed since the tragic events three years ago. "When life hands us something of this kind of magnitude, it changes every fiber of our being. And we can never go back to the way we were before, no matter how much we may want to at times," Gregory wrote in her post.
People across the city will also be taking part in blood drives, food and clothing donations and other community service projects to pay tribute to Boston and those affected marathon bombings. See how some are giving back for One Boston Day below:
"Today we honor those who came from all over the country to donate blood at MGH on 4.15.13. Stop by the MGH Blood Donor Center today and do a good deed this #OneBostonDay"
".@REALSlyde has arrived at the #hotel dropping off the #NERevs' #OneBostonDay sneaker donation for @SFHBoston. @nerevolution #hyattruns We cannot thank you enough!"
"We are recognizing #OneBostonDay by kicking off a sock drive for Boston Health Care for the Homeless. Our collection bin is in the Seaport Hotel lobby through April 29th or you may "valet" socks by driving up to the front door of the hotel; our doormen are happy to collect them! Help us fill our bin! #socks #homeless #bostonstrong"
"Received a great note with a hand made flower from some pretty great kids! Today is "One Boston Day" we celebrate with a flower to help you remember that you are Special and Loved."
"It's #OneBostonDay and associates are handing out #MarathonDaffodils as a symbol of hope along the race route."
"Today we celebrate #OneBostonDay with random acts of kindness and goodwill. Take a moment to thank our #veterans with a letter for the New England Center and Home for Veterans. #BostonStrong #PayItForward #NeverForget #NECHV"
"Your old sneakers deserve a new home. Donation boxes placed at the #BostonMarathon Jumbotron, at the intersection of Boylston & Exeter Streets, will collect shoes for the residents of St. Francis House from 11am-2pm on Friday, April 15th. #OneBostonDay"
The Associated Press contributed to this report.