For 17 years, a plaque at the Halifax Explosion memorial site in Fort Needham park has told passersby about the disaster that rocked the port city on Dec. 6, 1917.

"Reversing her engines, Mont-Blanc went astern to pull out the deep gash in Imo's side," the plaque reads. 

"Steel rasped against ragged steel, sparks flew, Mont-Blanc caught fire and blew up at 9:04:35 a.m." 

The trouble is that the plaque has the story wrong.

"As everybody knows, the Imo rammed into the Mont-Blanc," said Allan Rodger, who was walking through the park recently and noticed the error. 

"This plaque says the exact opposite." 

Halifax Explosion

The Imo actually rammed into the Mont-Blanc. (CBC)

History-making blast

The collision in Halifax harbour between the Belgian relief vessel Imo and the Mont-Blanc, a French cargo ship loaded with explosives, led to the largest man-made explosion in the world before the atomic bomb.

The explosion ripped through the city, killing and wounding thousands of people. The city's north end — where Fort Needham Memorial Park is now found — was especially devastated.

In 1942, the park was established by the Halifax Relief Commission to commemorate the victims of the explosion. Every year, on the anniversary of the disaster, a service of remembrance is held at the park's bell tower.

Rodger said he had just finished reading Aftershock, a non-fiction book by Halifax author Janet Maybee, when he visited the park. The book chronicles how the harbour pilot of the Mont-Blanc, Francis Mackey, was wrongly persecuted for causing the explosion. 

Its pages include a picture of the park's plaque, put in place by the city's millennial advisory committee at the turn of the century, and also points out the ship's names are reversed.

Maybee wasn't the first expert to notice the error. 

Error hasn't gone unnoticed

The CBC contacted several people, including Janet Kitz, a researcher and expert on the explosion. 

"The sign is wrong and should be changed," said Kitz. "It has the boats mixed up."

A few metres away, attached to the larger monument, another plaque has the correct information inscribed on it.

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The Belgian steamship Imo was beached on Dartmouth shore after the 1917 Halifax explosion. Its collision with the munitions ship Mont-Blanc sparked the fire that set off the explosion. (Nova Scotia Archives & Record Management/Canadian Press)

"It's an honest mistake, but it should be rectified," said Joel Zemel, a Halifax Explosion expert and author of Scapegoat: The Extraordinary Legal Proceedings Following the 1917 Halifax Explosion

"Every historical situation you're bound to run into this sort of situation. The idea is to get sources whereby someone can do the research and find the truth." 

Zemel, who lives in Halifax, hopes that planned upgrades to the park for the 100th anniversary of the explosion will include changing or removing the sign.

The word phoenix is also misspelled "phoneix" on the sign.

Changes are coming

Municipal spokesman Brendan Elliott said officials are aware of the error and the marker will be removed as part of the upgrades.

"The municipality will verify all interpretive information to be included in the park through the Nova Scotia Archives as well as through our own municipal archives to ensure accuracy," he said in an email.

Work is to begin later this year on a $2.7-million revitalization of the park.