On December 6 , 1917 at 9:04:35 am , the Halifax Explosion severely destroyed much of the city , by the largest man-made explosion up to that time . Boston authorities learned of the disaster by telegraph , and quickly organized and dispatched a relief train around 10 pm to assist survivors . A blizzard delayed the train , which finally arrived in the early morning of December 8 , and immediately began distributing food , water , and medical supplies . Numerous personnel on the train were able to relieve the Nova Scotia medical staff , most of whom had worked without rest since the explosion occurred . Nova Scotian children study the explosion in school and they know " Boston was one of the first responders , and really a lifesaver . " Nova Scotia donated a large Christmas tree to the city of Boston in thanks and remembrance for the help Boston Red Cross and the Massachusetts Public Safety Committee provided immediately after the Halifax Explosion of 1917 . Another tree was sent in 1971 , and every year since
Halifax Explosion
Halifax Explosion
Boston Christmas Tree