1917 – Halifax Explosion: the largest artificial explosion up to that time

6 December

The Halifax Explosion was a maritime disaster in Halifax, Nova Scotia, Canada, on this day in 1917. SS Mont-Blanc, a French cargo ship laden with high explosives, collided with the Norwegian vessel SS Imo in the Narrows, a strait connecting the upper Halifax Harbour to Bedford Basin. A fire on board the French ship ignited her cargo, causing a large explosion that devastated the Richmond district of Halifax. Approximately 2,000 people were killed by debris, fires and collapsed buildings, and an estimated 9,000 others were injured.

Mont-Blanc was under orders from the French government to carry her cargo of high explosives from New York via Halifax to Bordeaux, France. At roughly 8:45 am, she collided at low speed (approximately one knot (1 to 1.5 miles per hour or 1.6 to 2.4 kilometres per hour)) with the unladen Imo, chartered by the Commission for Relief in Belgium to pick up a cargo of relief supplies in New York. The resulting fire aboard the French ship quickly grew out of control. Approximately 20 minutes later at 9:04:35 am, Mont-Blanc exploded. The blast was the largest man-made explosion prior to the development of nuclear weapons, releasing the equivalent energy of roughly 2.9 kilotons of TNT.

Nearly all structures within a half-mile (800 m) radius, including the entire community of Richmond, were obliterated. A pressure wave snapped trees, bent iron rails, demolished buildings, grounded vessels, and scattered fragments of the Mont-Blanc for kilometres. Hardly a window in the city proper survived the blast. Across the harbour, in Dartmouth, there was also widespread damage. A tsunami created by the blast wiped out the community of Mi'kmaq First Nations people who had lived in the Tuft's Cove area for generations.

Relief efforts began almost immediately, and hospitals quickly became full. Rescue trains began arriving from across eastern Canada and the north-eastern United States, but were impeded by a blizzard. Construction of temporary shelters to house the many people left homeless began soon after the disaster. The initial judicial inquiry found the Mont-Blanc to have been responsible for the disaster, but a later appeal determined that both vessels were to blame. There are several memorials to the victims of the explosion in North End.