On this day in 1907, the south arm of the Quebec Bridge went into the St Lawrence River while it was still being built. Seventy-five men were killed. Thirty-three of them were Mohawk ironworkers from Kahnawake.
What stood there that afternoon was a cantilever reaching out from the south shore over open water, the longest span anyone had yet attempted: steel chords in compression, riveted lattice, a travelling crane out at the end adding its own load to the arm it was extending. The dead weight of that steel had been reckoned too low in the calculations, and the structure was carrying more of itself than the figures allowed. Chords near the pier had begun to bend in the days before. The fall took seconds.
The men were riveters, fitters, crane hands, the ones who walk out on steel that is not finished yet because someone must. Kahnawake is a small place, and it lost thirty-three of them in a single afternoon; the community keeps their names, and has kept them for more than a century. The bridge failed again in 1916, and eighty-eight lives were lost across the two collapses before it opened in 1919. When you cross it, that is who is under you.
Quietly, for the record: the bridge that stands there now was completed in 1917 and opened to traffic in 1919, and its centre span of about 549 metres is still the longest cantilever span in the world. The men who died built the knowledge that made it stand.
The royal commission found that the dead-weight estimate made early in the design was never revised as the span grew heavier, and that no one held clear authority to stop the work when the chords began to bend. Independent checking of calculations, and a named engineer empowered to halt construction, came out of that finding.