The deadliest industrial accident in US history, the incident now known as the Texas City Disaster killed at least 581 people. It also represents one of the largest non-nuclear explosions in recorded history, after more than 2,000 tonnes of ammonium nitrate was accidentally ignited and exploded.
In April 1947, the French-registered SS Grandcamp arrived at the port of Texas City in Galveston Bay. It was then loaded with over 2,300 tonnes of ammonium nitrate. Loading of the explosive chemical compound, uses as fertiliser or in the manufacturing of explosives, had been banned at some other ports, including Houston.
The Grandcamp was constructed as part of the ‘Liberty Ship’ scheme that saw the US commission large numbers of low-cost, simply constructed ships to serve in the Second World War. After serving the Pacific Theatre, the ship originally named the SS Benjamin R Curtis was reassigned to France and renamed. Alongside the shipment of ammonium nitrate, the Grandcamp was also carrying ammunition and machinery.
At around 8am on April 16th, smoke was seen emanating from the cargo hold of the Grandcamp. Several attempts to extinguish the fire failed. An attempt to extinguish the fire by flooding the hold with steam is likely to have contributed to the explosion, as the steam reacted with the ammonium nitrate to create nitrous oxide.
The efforts of firefighters, dock workers and crew to extinguish the fire drew a large crowd of spectators. More were drawn as the steam pressure blew open hatches and the ship began emitting thick yellow smoke. Some spectators noted that the water around the ship was beginning to boil.
At 9:12am, the ammonium nitrate exploded through a combination of heat and pressure. The blast produced a shockwave that was felt even 100 miles out to sea. Around the docks, over 1,000 buildings were flattened. A plant owned by Monstanto Chemical Company was ignited, causing secondary explosions as refineries and chemical tanks blew up.
Two passing planes were blown out of the sky, and windows in the surrounding area were shattered in a 10 miles radius. Berthed 600 metres away, the SS High Flyer and her cargo of more ammonium nitrate and over 1,800 tonnes of sulfur also detonated. One of her propellers was found nearly a mile inland. The anchor of the Grandcamp landed over 1.6 miles away.
The initial official estimate ran to 567 dead, including the crew of the Grandcamp and all but one of the Texas City fire department. The cause of the fire has never been determined, although one theory is that it was started by a discarded cigarette end. 63 of the victims (the death toll was later revised to 581) have never been identified. 113 other victims were never found. It may be that the death toll was higher, as there were likely visiting seamen and other travelers that were not accounted for in official records.
Around 5,000 people were injured, with more than 2,000 rendered homeless after their houses were demolished. Property damage overall totalled around $100 million, the equivalent of $1.2 billion today. The site where Grandcamp’s two-tonne anchor landed is now a memorial park.