At 8:45 a.m. on December 6, 1917, a Belgian relief ship, the Imo, and a French munitions ship, the Mont Blanc, collided in Halifax harbour as a result of human error. At 9:06 a.m., the Mont Blanc’s cargo ignited, triggering the largest human-created explosion before the atomic bombing of Hiroshima in 1945. Over 2.5 square kilometres of the north end of Halifax were levelled by the blast, as buildings were flattened, windows were shattered and fires broke out among the ruins. Survivors’ accounts emphasize how families were torn apart by the blast: in some cases, children survived while their parents were killed, and in others families of eight or nine had only one or two survivors. Fortunately, news of the explosion spread quickly, and nearby communities, provinces and states promptly dispatched medical personnel, materials and money to help the suffering and rebuild the city. Ultimately, governments, businesses and individuals donated over $30 million and the city recovered. This disaster highlighted the lack of a national health department or emergency plan and contributed to the creation of the federal Department of Health in 1919.