A Wave of Molasses: Boston's Strangest Disaster

Just after noon on 15 January 1919, workers near the Purity Distilling Company’s waterfront tank on Commercial Street, in Boston’s North End, heard a sound like machine-gun fire — the rivets letting go. The five-story steel tank tore open, and roughly 2.3 million gallons of molasses surged into the streets in a wave witnesses put at some 25 feet high. [1]

Sweet cargo, deadly force

Molasses was serious industry in 1919: it was fermented into industrial alcohol, an ingredient of munitions during the First World War, and the tank had been topped up with a fresh, warm shipment only days before. [2] The wave moved with astonishing speed for so viscous a fluid — enough to buckle the steel supports of the Boston Elevated Railway trestle on Atlantic Avenue, knock buildings off their foundations, and bury horses, wagons, and people. Twenty-one people were killed and about 150 injured. [1] Rescuers spent days cutting victims and survivors out of the hardening brown mass, and the harbor ran brown for months.

Why the tank failed

The tank had been built hurriedly in 1915 and was never properly tested — it was filled with only a few inches of water before being put into service, and it leaked so visibly that the company painted it brown. [2] Later analysis found the steel walls too thin for the load. A sudden warm spell that week — temperatures had climbed dramatically in the days before the collapse — may have raised the internal pressure of the recently mixed molasses, adding the final stress. [2]

The lawsuit that set a precedent

The disaster produced one of the era’s most consequential legal reckonings. Victims and their families brought a consolidated set of claims against United States Industrial Alcohol, Purity’s parent company, which insisted the tank had been dynamited by anarchists. After years of hearings and testimony from hundreds of witnesses, the court-appointed auditor Hugh W. Ogden found the company responsible for the tank’s inadequate construction, and it paid out settlements reported at around $628,000 — real money in the 1920s. [1] [3]

The lesson poured into law

The finding helped establish that corporations could be held to account for engineering decisions, and it pushed Boston — and, in time, other American jurisdictions — toward requiring that engineers’ and architects’ plans be certified and inspected before construction. [2] The strangest disaster in Boston’s history thus left an entirely serious legacy: the modern expectation that a structure must be shown to be safe before it is filled.