On December 6, 1917, the Mont-Blanc, a French freighter carrying nearly 2,900 tonnes of explosives, collided with the Imo, a Norwegian ship, in the Narrows channel near Halifax, Nova Scotia. The collision occurred at a slow speed of about one knot, less than 2 km/h, at around 8:45 am. The Mont-Blanc had arrived from New York, while the Imo was heading to Bedford Basin to pick up supplies. The accident was the result of a series of poor navigational decisions at the entrance of the Narrows. The Mont-Blanc carried a dangerous cargo, including 2,300 tonnes of picric acid, 200 tonnes of TNT, and 10 tonnes of fulminate of mercury, along with barrels of benzol on the deck. The impact damaged the barrels, allowing flammable vapors to escape and ignite, likely from sparks. The Mont-Blanc’s crew abandoned the ship without successfully warning the port, and all French sailors except one survived, while six men from the Imo died. The burning ship drifted toward dock number 6, where curious residents gathered on the docks, in the streets, and at windows. Only a few naval officers recognized the danger. At 9:04 and 35 seconds, the Mont-Blanc exploded with a force estimated at 2.9 kilotons of TNT, making it the largest human-made explosion before the atomic bomb. Almost all structures within 800 meters were destroyed. A 1,140-pound anchor piece was projected nearly four kilometers, roughly twice the distance between the Eiffel Tower and the Saint-Lazare station in Paris. Windows shattered within an 80 km radius, and many people standing behind their windows were injured by flying shards. According to History.com, about 200 people were permanently blinded, while other sources suggest higher numbers. A wave of about two meters hit the shores, followed by fires that further devastated the area. The confirmed death toll was 1,782, with about 9,000 injured, though some estimates suggest the number of dead may be higher. Approximately 1,630 houses were destroyed, leaving 6,000 people homeless. Adjusting for the size of the city, the impact was devastating. One minute after the explosion, one in five residents of Halifax was dead or injured, according to Slate. Some victims were so severely affected that their bodies were unrecognizable, and one was not identified until 1919. Boston and Massachusetts responded with solidarity, and a judicial investigation initially blamed the Mont-Blanc, but an appeal concluded both ships shared responsibility. The neighborhoods destroyed by the explosion were rebuilt with improved safety standards, and the event spurred advances in medicine, social assistance, and public health. Every December 6 at 9 o’clock, the bells of the Memorial Bell Tower ring to honor the victims. Canadians consider it the most serious accident in their history. In gratitude for Boston’s help, Nova Scotia sends a large Christmas tree to Boston every winter, a tradition that continues to this day.