Halifax Explosion of 1917: When Two Ships Shattered a City

Imagine having an earthquake, flood, and a tornado at the same time. That is the closest way I know to describe what happened. At first I thought many of the stories were exaggerated; they most certainly were not. This one goes way beyond two ships colliding. The echoes of this event are still being felt today in 2026.

After reading several articles about the Halifax Explosion, I came across a book called The Great Halifax Explosion: A World War I Story of Treachery, Tragedy, and Extraordinary Heroism by John U. Bacon. I would strongly recommend it to anyone interested in learning more about this event and its place in Canadian history.

For twenty minutes, the citizens of Halifax, Nova Scotia watched a ship burn. People gathered along the waterfront and stood at their windows to see what was happening. Almost none of them knew that the ship carried roughly 2,500 tons of explosives.

On the morning of December 6, 1917, the busy port city of Halifax, Nova Scotia, became the site of the Halifax Explosion. It was the largest human-made explosion in history prior to the development of atomic weapons. During World War I, Halifax served as a critical logistical hub for sending troops, supplies, and munitions to Europe.

The disaster began shortly before 9:00 a.m. when the SS Mont-Blanc, a French cargo ship loaded with military explosives, including TNT and picric acid, collided with the SS Imo, a Norwegian ship heading to New York to collect relief supplies for Belgium. Ships carrying explosives normally flew a red warning flag, but that practice had been relaxed during the war to avoid advertising their cargo to German submarines. Mont-Blanc flew no such flag to warn others of the explosives in her holds.

The collision occurred in the Narrows, a tight channel connecting the upper and lower sections of Halifax Harbour. While the impact itself was relatively minor, it damaged barrels of benzol (airplane fuel) stored on Mont-Blanc’s deck. The highly flammable liquid spilled across the ship, and a fire broke out. Recognizing the danger, the French crew abandoned ship, leaving the burning, unanchored ship to drift toward the waterfront. The crew tried to warn people of the danger, but their warnings went largely unheeded. The language barrier and also, it was hard to hear these men in the water.

Railway dispatcher Vince Coleman was warned that the burning Mont-Blanc could explode at any moment. He started to leave but returned to his telegraph to warn incoming trains. He was especially concerned about a train approaching Halifax with about 300 people aboard. Coleman was killed in the explosion. His warning reached railway stations outside the city and helped bring relief trains carrying medical staff, firefighters, and supplies.

Around 9:05 a.m., Mont-Blanc detonated with the force of roughly 2.9 kilotons of TNT. The blast flattened more than a square mile of Halifax, particularly devastating the working-class Richmond district. The shockwave ripped through the region, shattering windows miles away and hurling parts of the ship into the surrounding countryside. The explosion also generated a powerful wave, reported to have reached nearly 50 feet in some places. It swept onto the shorelines of Halifax and Dartmouth, drowning people who had survived the initial blast.

A huge mushroom-shaped cloud rose above the harbor. Witnesses also described a strange, dark rain falling after the explosion. Smoke, soot, dust, and debris from the destruction filled the air and fell across parts of the devastated city.

The immediate aftermath of the explosion was a scene of devastation, resulting in approximately 2,000 deaths and an estimated 9,000 injuries. Flying glass from shattered windows caused widespread injuries, including severe eye damage and permanent loss of sight. Fires broke out across the damaged wooden neighborhoods, compounding the disaster. A severe blizzard struck the region the following day, dumping heavy snow that hampered rescue efforts and exposed injured and homeless survivors to bitter cold.

Despite the overwhelming tragedy, a massive relief effort quickly formed. Emergency workers, medical personnel, and supplies arrived from across Canada and the United States. Massachusetts organized a relief train carrying doctors, nurses, and supplies, which departed Boston that evening. In a lasting symbol of gratitude for American assistance, Nova Scotia continues the tradition of sending a Christmas tree to Boston each year.

The recovery process eventually reshaped Halifax. It led to the construction of the historic Hydrostone neighborhood, built with fire-resistant materials as part of the city’s reconstruction. The disaster also exposed serious gaps in harbor safety. The subsequent inquiry called for clearer rules governing ships carrying explosives.

Here is a passage from the John Bacon book: With the final addition of the benzol, Mont Blanc now carried an impressive array of the most dangerous chemicals known to man at that time. While benzol can’t match the pure power of gun cotton, TNT, or picric acid, all high explosives, what the stevedores probably didn’t know when they stacked the barrels of benzol on deck was that the airplane fuel needed only a spark to ignite, while picric acid doesn’t explode until it reaches 572 degrees Fahrenheit, and TNT does not detonate until it reaches 1,000 degrees. But by making the last-minute decision to store most of the fuel on the deck and the TNT and picric acid below, the crew had unwittingly constructed the perfect bomb, with the easy-to-light fuse on top, and the most explosive materials trapped in the hold below.

For some personal stories, go to the companion page! There are some very interesting human stories.

The SS Mont-Blanc‘s anchor (about 1,140 pounds) was hurled 2.35 miles, and now it’s a memorial.