Great Molasses Flood, Boston, 1919

A steel tank fifteen metres high, holding about nine million litres of molasses, stood on the harbour front in a crowded Italian immigrant district. It had leaked since the day it was filled — the company had painted it brown so the seepage would not show, and local children collected the drips in cans. On an unusually warm January afternoon it split apart. The wave was several metres high and moved faster than a person can run, carrying away a fire station, buckling the elevated railway and crushing houses.

Twenty-one people died and about a hundred and fifty were injured; some bodies were not recovered for days, and the harbour ran brown until summer. The company blamed anarchists. The court case that followed ran for years and produced one of the earliest class actions in Massachusetts; the auditor found the tank had never been tested, its steel was too thin, and no engineer or architect had checked the design. The verdict against the company helped establish that builders must have their work certified by qualified engineers — a rule now general. A small plaque marks the site.