Clutching candy cane balloons, sipping hot chocolate and singing along to Jingle Bells, thousands rejoiced on Boston Common Thursday night for the city’s official Christmas tree lighting.
Santa Claus got the biggest cheers as he arrived on stage at 8 p.m. to help light the tree with Mayor Martin J. Walsh and Nova Scotia Premier Stephen McNeil.
The city and Canadian province are celebrating a century of a special friendship born out of tragedy. On Dec. 6, 1917, a devastating explosion in Halifax Harbour killed 2,000 people and injured 9,000 more.
Boston answered a call for emergency aid, and sent a medical team and supplies by train through a blinding blizzard. As a thank you for Boston, Nova Scotia next year sent a Christmas tree to the city. A second tree was sent in the 1970s, and every year that’s followed.
On Thursday, Boston and Nova Scotia marked 100 years of their special bond with the tree lighting and the unveiling of a new monument on the Common.
Walsh, McNeil and Halifax Mayor Michael Savage gathered earlier Thursday to unveil a plaque at the location of the Christmas tree, behind the Park Street T Station at the intersection of Park Street and Tremont Street.
“Visitors who come here will learn about the special bond our cities share, and about the strength and resilience of the human spirit,” Walsh said. “We set an example for the rest of the world on how we can take care of each other, especially at a time of need.”
McNeil also acknowledged the role Boston played in helping Halifax 100 years ago.
“When we called out, it was the people of Boston who responded to our needs,” he said.
This year’s tree was dedicated to first responders in both cities, McNeil said. Nine first responders from Nova Scotia attended the unveiling, and McNeil commended them and their predecessors.
“Imagine the devastation that was taking place in the north end of our city, and our first responders . . . were heading in to see what they could do for their fellow citizens,” he said.
Beth Thomson, a registered nurse whose parents lived in Halifax at the time of the disaster, said the tragedy shaped her path to nursing.
Thomson’s mother was arriving at her elementary school when two ships collided in Halifax Harbour, triggering the explosion.
“Her world burst opening with a big cloud of smoke,” she said. “She thought God was punishing her for being late for school.”
When the glass windows in her father’s classroom shattered, he thought the Germans were attacking, Thomson said.
Here father worked on the streets for three days to help those in need, she said. Her mother saw those efforts, and they inspired her to move to Massachusetts years later and enroll in nursing school.
The two met when Thomson’s father also moved to the commonwealth and married shortly after.
Savage, the Halifax mayor, shared a story of a woman named Mary Jean Hinch who lost her family in the explosion.
Hinch woke up that day and sent her 10 children to school, but when the dust settled the next day, “she lost six siblings, her mother, her 10 children, and her husband,” Savage said.
She was pulled from a pile of rubble and snow, and a few months later, she gave birth.
“That is the scope of the Halifax explosion,” he said.Jake Johnson can be reached at Jake.Johnson@globe.com Alyssa Meyers can be reached firstname.lastname@example.org. Follow her on Twitter @ameyers_.