The tank stood on Commercial Street in Boston’s crowded, largely Italian-immigrant North End: 50 feet tall, 90 feet in diameter, built in 1915 by the Purity Distilling Company, a subsidiary of United States Industrial Alcohol. It held molasses awaiting distillation into industrial alcohol — a key ingredient in munitions manufacturing during the First World War.
The tank had leaked from the day it was filled. Residents collected the seepage in cans. The company’s response was to paint the tank brown so the leaks would show less.
15 January 1919
The day was unseasonably warm — around 4°C after a stretch of deep cold. Two days earlier the tank had been topped up with a fresh, warm shipment of molasses from Puerto Rico, bringing the contents to approximately 2.3 million gallons (8.7 million litres).
At about 12:30 the tank failed catastrophically. Witnesses described a sound like machine-gun fire as the rivets sheared, then a low roar. A wave of molasses — estimated at 25 feet high at its front, moving at roughly 35 mph — swept across Commercial Street.
The wave crushed the wooden Engine 31 firehouse, snapped the steel supports of the elevated railway, and flattened tenements. Horses, wagons, and people were engulfed where they stood. Molasses at that scale does not behave like syrup on a spoon: the initial wave struck with the force of moving concrete, and as it cooled it stiffened around the trapped.
21 people died — some crushed, most suffocated. About 150 were injured. Rescue workers, cadets from the USS Nantucket, and Red Cross nurses waded chest-deep for days. The last body was recovered nearly four months later.
The reckoning
United States Industrial Alcohol blamed anarchist saboteurs. The class-action suit that followed — one of the first major ones against a US corporation — ran six years. Auditor Hugh Ogden heard some 3,000 witnesses before finding the company fully liable in 1925: the tank had been built too thin, never inspected by an engineer, and never tested full with water. The company paid out around $628,000 in damages.
The case helped establish modern engineering certification requirements for construction in Massachusetts and beyond. Local legend holds that on hot days the North End still smells faintly of molasses.