On the morning of 6 December 1917, the French cargo ship SS Mont-Blanc and the Norwegian vessel SS Imo collided in the harbour of Halifax, Nova Scotia, Canada. Laden with high explosives, Mont-Blanc caught fire and detonated, devastating the Richmond district of Halifax. At least 1,782 people, largely in Halifax and Dartmouth, were killed by the blast, debris, fires, or collapsed buildings, and an estimated 9,000 others were injured. The blast was the largest human-made explosion at the time.
A busy wartime harbor
Dartmouth lies on the east shore of Halifax Harbour, and Halifax is on the west shore. By 1917, "Halifax's inner harbour had become a principal assembly point for merchant convoys leaving for Britain and France." Halifax and Dartmouth had thrived during times of war; the harbour was one of the British Royal Navy's most important bases in North America, a centre for wartime trade, and a home to privateers who harried the British Empire's enemies during the American Revolution, the Napoleonic Wars, and the War of 1812. The completion of the Intercolonial Railway and its Deep Water Terminal in 1880 allowed for increased steamship trade and led to accelerated development of the port area. The British garrison left the city in late 1905 and early 1906, and the Canadian government took over the Halifax Dockyard (now CFB Halifax).
Halifax Dockyard later became the command centre of the Royal Canadian Navy (RCN) on its founding in 1910. Just before the First World War, the Canadian government began a determined, costly effort to develop the harbour and waterfront facilities. The outbreak of the war brought Halifax back to prominence. As the RCN had virtually no seaworthy ships of its own, the Royal Navy assumed responsibility for maintaining Atlantic trade routes by readopting Halifax as its North American base of operations. In 1915, management of the harbour fell under the control of the RCN; by 1917, the naval fleet in Halifax was growing, including patrol ships, tugboats, and minesweepers.
Collision, fire, and explosion
Imo was granted clearance to leave Bedford Basin by signals from the guard ship HMCS Acadia around 7:30 on the morning of 6 December, with Pilot William Hayes on board. The ship entered the Narrows well above the harbour's speed limit in an attempt to make up for the delay experienced in loading her coal. Imo met American tramp steamer SS Clara being piloted up the wrong (western) side of the harbour. The pilots agreed to pass starboard-to-starboard.
Soon afterwards, Imo was forced to head even further towards the Dartmouth shore after passing the tugboat Stella Maris, which was travelling up the harbour to Bedford Basin near mid-channel. Horatio Brannen, the captain of Stella Maris, saw Imo approaching at excessive speed and ordered his ship closer to the western shore to avoid an accident. At 9:04:35 am, the out-of-control fire on board Mont-Blanc set off her cargo of high explosives.
The ship was completely blown apart and a powerful blast wave radiated from the explosion, initially at more than 1,000 metres (3,300 ft) per second. Temperatures of 5,000 °C (9,000 °F) and pressures of thousands of atmospheres accompanied the moment of detonation at the centre of the explosion. White-hot shards of iron fell down upon Halifax and Dartmouth. A cloud of white smoke rose to at least 3,600 metres (2,000 fathoms; 11,800 ft).
Rescue and rebuilding
First rescue efforts came from surviving neighbours and co-workers, who pulled and dug out victims from buildings. The initial informal response was soon joined by surviving policemen, firefighters, and military personnel who began to arrive, as did anyone with a working vehicle; cars, trucks and delivery wagons of all kinds were enlisted to collect the wounded. A flood of victims soon began to arrive at the city's hospitals, which were quickly overwhelmed. The new military hospital, Camp Hill, admitted about 1,400 victims on 6 December.
Firefighters were among the first to respond to the disaster, rushing to Mont-Blanc to attempt to extinguish the blaze before the explosion even occurred. They also played a role after the blast, with fire companies arriving to assist from across Halifax, and by the end of the day from as far away as Amherst, Nova Scotia, (200 kilometres or 120 miles) and Moncton, New Brunswick, (260 kilometres or 160 miles) on relief trains. Efforts began shortly after the explosion to clear debris, repair buildings, and establish temporary housing for survivors left homeless by the explosion.
By late January 1918, around 5,000 were still without shelter. A reconstruction committee under Colonel Robert Low constructed 832 new housing units, which were furnished by the Massachusetts-Halifax Relief Fund. Partial train service resumed from a temporary rail terminal in the city's South End on 7 December. Full service resumed on 9 December when tracks were cleared and the North Street Station reopened.