Boston has received a Christmas tree from Halifax, Nova Scotia every year since 1971, as a thank you for assisting Halifax after the Halifax Explosion of 1917.
According to the official Nova Scotia website, on December 6th, 1917, the Norwegian supply ship Imo collided with the French munitions ship Mont-Blanc, causing the largest man-made explosion the world had ever seen. Close to 2,000 people were killed, hundreds wounded, 1,600 homes were destroyed. The city of Boston dispatched a relief train that night to assist survivors and helped with the rebuilding process.
The following year, in 1918, Halifax sent a Christmas tree to Boston to thank them for their kindness, and the gift was revived in 1971.
This year's Christmas tree is a 43 foot, 55-year-old, white spruce from John MacPherson and Ethel Ann's backyard in Antigonish, Nova Scotia. The tree actually has a twitter handle.
To learn more about the Halifax Explosion, go here.