The Great Molasses Flood: Boston 1919

The Tank

The Purity Distilling Company operated a giant molasses storage tank in the North End of Boston. The tank had been leaking for months. Residents had complained about the smell. Children in the neighbourhood regularly collected molasses from cracks in the tank wall. The company painted the tank brown to hide the leaks rather than fix them.

On 15 January 1919, another shipment of molasses arrived, filling the tank close to capacity. At 12:30 in the afternoon the tank burst.

The Wave

2.3 million gallons of molasses flooded into the streets of the North End. The wave was approximately 15 feet high and moved at an estimated 35 miles per hour — faster than a person could run. It demolished buildings, lifted a freight train off its tracks, and killed 21 people. A further 150 were injured.

Civilian deaths occurred from the chaos and panic of the blackout as much as from the wave itself. The city smelled of molasses for decades afterwards, particularly in warm weather.

The Legal Battle

119 residents filed a class action lawsuit against the United States Industrial Alcohol Company — one of the first class action suits in Massachusetts history. The company's defence strategy included suggesting that anarchists had sabotaged the tank, attempting to deflect blame during the first Red Scare. The court rejected this argument entirely. After years of proceedings the company was ordered to pay damages.

No individuals were ever criminally charged. The company paid out in the civil case but nobody responsible for the ignored warnings or the decision to conceal the leaks faced personal criminal consequences.

The Mechanism

The Great Molasses Flood is studied in engineering ethics as a case of what happens when safety warnings are systematically ignored and accountability is absent. The tank had been poorly designed, was known to be leaking, had been painted to conceal the problem rather than fix it, and was overfilled. The disaster was not an accident. It was the result of a sequence of decisions — each with a justification — that nobody chose to reverse.