Quebec Bridge collapsed during construction — 1907 and again in 1916 — killing 88

The Quebec Bridge was to be the longest cantilever span in the world — 549 metres across the St. Lawrence River, linking Quebec City to Lévis. The Quebec Bridge and Railway Company hired the Phoenix Bridge Company to fabricate and erect the steelwork, and Theodore Cooper, a retired US Army engineer with an excellent reputation, as consulting engineer. Construction began in 1900, but by 1907 the project had consumed more steel than the original design allowed for and the dead load had grown dangerously high.

That summer, workers noticed that lower chords in the cantilever arms were beginning to buckle — the steel was distorting under the weight of the structure itself. Engineers on site wrote to Cooper, who was in New York, asking whether to stop work. Cooper approved continued loading. On 29 August 1907, as workers were adding the final steel on the south cantilever arm, the entire south half of the bridge gave way. Of the 86 men on the span, 75 fell into the river and died. Thirty-three of them were Mohawk steelworkers from the Kahnawake reserve.

A Royal Commission of three engineers reported on 20 February 1908, assigning responsibility to errors in judgment by Theodore Cooper and Peter L. Szlapka of Phoenix Bridge. The dead load had been seriously underestimated, those calculations were never independently checked, and the Quebec Bridge and Railway Company had failed to appoint an experienced chief engineer. A new, heavier design was commissioned. On 11 September 1916, as the new central span was being raised, a casting in the erection equipment failed and the span fell, killing another 13 workers.