At 2:50 p.m. - exactly one week after the bombings - many bowed their heads and cried at the makeshift memorial on Boylston Street, three blocks from the site of the explosions, where bouquets of flowers, handwritten messages, and used running shoes were piled on the sidewalk.
Bridget Horne, 28, who finished the marathon minutes before the explosions, spent the moment of silence locked in a group hug with other survivors.
Horne, clad in her bright-blue marathon jacket, had run to Boylston Street from her South Boston office with several colleagues to mark the moment. It was her first time returning to the scene since the day of the attack.
"I just need to be with people who were there," she said.
Two bombs exploded a week ago Monday as runners were crossing the finish line about four hours into the marathon. Three people were killed and more than 180 were injured. Many lost limbs.
A little more than a mile away, hundreds of state employees gathered outside the Massachusetts Statehouse to observe the moment of silence.
Gov. Deval Patrick bowed his head, standing with Lt. Gov. Timothy Murray, Attorney General Martha Coakley, Secretary of State William Galvin and House Speaker Robert DeLeo on a landing on the great front steps of the capitol.
"God bless the people of Massachusetts. Boston Strong," Patrick said when the moment had ended.
The officials departed without any further words as church bells echoed across the city.
The silence was broken on Boylston Street when a Boston police officer pumped his fists in the air and the crowd erupted in applause.
They quietly sung 'God Bless America' before starting to leave the area.