"We will carry them in our hearts," he said.
Downes said the city on April 21 will "show the world what Boston represents." He added, "For our guardian angels, let them hear us roar."
Adrianne Haslet-Davis, a ballroom dancer who lost her left leg below the knee and has recently returned to performing on a prosthetic leg, said she's learned over the last year that no milestone is too small to celebrate, including walking into a non-handicapped bathroom stall for the first time and "doing a happy dance."
Gov. Deval Patrick spoke of how the attack has drawn people closer.
"There are no strangers here," he repeated throughout his speech.
Carlos Arredondo, the cowboy hat-wearing spectator who was hailed as a hero for helping the wounded after the bombings, said he went to the tribute ceremony to support survivors and their families.
"You can see how the whole community gathered together to support them and remember," Arredondo said.
After the tributes, many of those in attendance walked in the rain to the finish line for a moment of silence that coincided with the time when the bombs went off. Bells rang, and a flag was raised by transit agency police Officer Richard Donohue, who was badly injured during a shootout with the bombing suspects.
Earlier in the day, a wreath-laying ceremony drew the families of the three people killed last year — Martin Richard, Krystle Campbell and Lu Lingzi — and Collier's relatives.
Associated Press writer Philip Marcelo contributed to this report.