What did the Quebec Bridge disaster teach engineers, and is the iron ring really made from its steel?

The Quebec Bridge disaster taught engineers that a bridge's own weight must be calculated and double-checked, and that someone experienced must be in charge. It collapsed in 1907 because the early calculations were never properly checked and the bridge's dead load, its own weight, was far above what it could carry. The story that engineers still wear rings made from its steel is a myth, but the real lesson behind it is true and serious.

The warning signs were there. In the summer of 1907, as the bridge neared completion, engineers on site noticed key members bending out of shape. Theodore Cooper, the consulting engineer, agreed the issue was serious and telegraphed the builders to add no more load. His message was not passed on to Quebec before it was too late. On 29 August 1907, 75 of the 86 workers on the bridge were killed, making it the world's worst bridge construction disaster. Of the victims, 33 were Mohawk steelworkers from Kahnawake, buried there under crosses made of steel beams.

The Royal Commission that investigated found that it was a mistake not to appoint an experienced bridge engineer as chief engineer. The disaster showed the dangers of inadequately supervised work. A second attempt failed too: on 11 September 1916 the central span of the new bridge fell as it was being raised, killing 13 workers, because a casting in the erection equipment failed. The bridge was finally finished, and its centre span of 549 metres is still the longest cantilevered bridge span in the world.

Today Canadian engineers receive an Iron Ring in a private ceremony. Many people believe it was forged from the wreck, but the first rings were made by World War I veterans at a Toronto military hospital. The ring is a reminder of the obligations and ethics of the profession.