The city is hosting a number of events to celebrate Boston's resiliency and generosity, and well as to honor survivors and those who lost their lives because of the 2013 attack.
Martin Richard, Krystle Campbell, and Lu Lingzi were killed at the finish line.
MIT Police Officer Sean Collier was killed later in the week.
Boston Police Officer Dennis Simmonds was hurt during the Watertown shootout and died from those injuries about a year later.
One Boston Day was created in 2015 by then-Mayor Marty Walsh as a way to transform a negative event into a positive one. The day encourages people to perform acts of kindness, such as supporting a small business, donating to a local organization or donating blood.
The Red Cross held it's annual blood drive for One Boston Day at Big Night Live on Causeway Street from 10 a.m. to 3 p.m.
“One Boston Day is our opportunity to stand together in service to and in solidarity with others, showcasing what makes Boston so special," Boston Mayor Michelle Wu said. “Whether it’s thanking our frontline workers or leaving a friendly, encouraging note on the T for a fellow rider, we could all benefit from a little kindness.”
The city of Boston is encouraging people to share their acts of kindness with the world using the hashtag #onebostonday.
WBZ's James Rojas (@JamesRojasNews) reports