Yet the spectre of that atrocity was inescapable as crowds turned out in record numbers to watch a field expanded to 36,000, to include some 5000 runners who could not complete last year's race.
A year ago, when US President Barack Obama comforted a city in mourning, he raised its morale with the pledge: "You will run again."
Now the day had come when Boston ran again, to reclaim the streets for the world's oldest marathon. The emotion on such a charged occasion intensified as for first time since 1983, the men's event was won by an American, Meb Keflizighi, who finished in just two hours and eight minutes.
The 38-year-old, who arrived in the US as a refugee from Eritrea aged 12, dedicated his victory to those killed last year, whose names were written on his running vest. "I said I am going to use their energy to win it, and they were spectators with me," he said. "I am honoured to win today. The US gave me a chance and gave me hope."
Roaring him on at the finish line was a man in a cowboy hat waving American flags: Carlos Arredondo, who became one of the faces of the bombings after being photographed wearing the same hat as he pulled to safety a man whose lower legs had just been blown off.
Arredondo, a Costa Rican immigrant, had been giving away flags in honour of fallen US soldiers in Iraq, including his oldest son, when the blasts exploded. He said he was still haunted by his memories of that day last year and struggled to remain calm in large crowds. "But no way was I not coming back to the finish line for 2014," he said.
He was not "wasting any time or thoughts" on the alleged bombers, Tamerlan and Dzhokhar Tsarnaev, ethnic Chechen brothers who lived in Boston's sister city of Cambridge.
"I don't think about those criminals," he said. "My focus today is the amazing people who have done wonderful things, it's thinking about those who are still healing, still in pain. This marathon shows that we have won, we have defied and defeated the terrorists."
For many runners, the marathon was also unfinished business as they returned to a race that was interrupted by the bombing. Among them was Briton Peter Holton, 60, an accountant from Derby, who was 800m from the finish when the bombs went off. "I came back to show support and pay tribute to the people of Boston who were so great to us."
His first reaction when the race was stopped a year ago had been frustration and anger that he was not being allowed to complete it.
He could not take in the first reports of bomb explosions. "It was only when one of the runners turned to me and said, 'Well, at least we're alive', that it started to sink in," he said.
Security was tight: backpacks were banned as the bombers had planted home-made devices inside such bags.
Across the city, people wore "Boston Strong" shirts, or carried placards bearing the same two words that became the mantra-like rallying call to unify the city in the days after the atrocity.
On the eve of the marathon, thousands of runners went to pay their regards at a memorial - decorated with flowers and running shoes - to those killed. Next to four crosses bearing the names of the dead - the fourth a police officer shot dead three days later during the manhunt - a sign read: "We will never forget them".
