Today marks the 92nd anniversary of the Halifax Explosion. Estimates are that over 2000 people died and 9000 were injured in the explosion, caused by the collision of two ships in the harbour and the subsequent fire, which ignited the WWI-bound explosive carried by the French ship. More people from Nova Scotia died in the explosion than actually died in WWI. Its record as the largest accidental man-made explosion persists to this day–and a one-mile blast radius around the explosion was made uninhabitable.
There are a number of good sites with information about the disaster:
Regional Municipality of Halifax site
(thanks to Micaylah for reminding me of the anniversary!)