The Great Molasses Flood of 1919: Boston's Strangest Disaster

At 12:30 P.M., the Tank Exploded

On January 15, 1919, a steel storage tank holding approximately 2.3 million gallons of crude molasses ruptured catastrophically in the North End neighborhood of Boston, Massachusetts. The collapse sent a wave of molasses estimated at 25 feet high and traveling at up to 35 miles per hour surging through the surrounding streets. Twenty-one people died. One hundred fifty were injured. Buildings were swept off their foundations. Horses and other animals were trapped and drowned. The structural failure that caused it had been visible for years — and the company that owned the tank had done nothing.

The Tank and Its Owner

The tank was owned by the United States Industrial Alcohol Company (USIA), which used molasses to ferment industrial alcohol — used at the time primarily to produce munitions during World War I, and afterward for rum production. The steel tank, located at 529 Commercial Street on the Boston waterfront, stood 50 feet tall and 90 feet in diameter. It had been erected in 1915 and put into service with minimal engineering oversight. Workers and residents in the area had noticed for years that the tank leaked so severely that neighborhood children could collect molasses from the seams. The company reportedly painted the tank brown to hide the stains.

The tank was chronically overfilled and poorly constructed. The steel plates were too thin for the volume they held, and the rivets were inadequately sized. An independent engineering inspection was never completed before the tank went into commercial operation.

The Day of the Disaster

The temperature in Boston had risen unusually rapidly in the days before January 15 — from roughly -17°C (1°F) to about 4°C (40°F) within 24 hours. USIA had recently received a fresh shipment of molasses from Puerto Rico, filling the tank nearly to capacity. The combination of fermentation-generated CO2 pressure, the temperature change causing thermal expansion of the liquid, and the tank's structural deficiencies proved catastrophic.

• Tank capacity: approximately 2.3 million gallons
• Wave height: estimated at 25 feet at its peak
• Wave speed: approximately 35 mph initially
• Area affected: approximately two city blocks
• Rescue operation: lasted days; some bodies were found under debris weeks later

The wave demolished a section of the Boston Elevated Railway structure, crushed firehouses and warehouse buildings, and buried workers at the nearby city yards under several feet of molasses. Rescue workers, many from the Navy and Red Cross, waded through waist-deep molasses for hours.

Deaths, Injuries, and Property Damage

The physical cleanup required workers using saltwater hoses, sand, and sawdust over a period of weeks. The molasses that reached Boston Harbor reportedly turned the water brown for months.

The Legal Battle

The disaster triggered one of the largest and most complex civil lawsuits in Massachusetts history. More than 119 plaintiffs brought claims against USIA. The litigation lasted six years. USIA initially attempted to blame the disaster on anarchists, claiming a bomb had been planted in or near the tank — an accusation shaped by the political climate of the Red Scare and recent anarchist bombings nationwide. The defense was ultimately rejected.

A court-appointed auditor named Hugh Ogden reviewed approximately 45,000 pages of testimony over three years and concluded that USIA bore full responsibility. The company had failed to conduct adequate engineering tests, had ignored evidence of structural deficiencies, and had prioritized production over safety. In 1925, USIA was ordered to pay approximately $628,000 in settlements to claimants — equivalent to roughly $11 million in 2024 dollars.

Legacy in Engineering and Law

The Great Molasses Flood accelerated the professionalization of structural engineering oversight in Massachusetts. Following the disaster, the state began requiring that building plans be certified by licensed engineers — a regulatory shift that influenced industrial construction standards across the country. The case also became an early example of successful corporate liability litigation in the United States for industrial negligence.

Myths and Persistent Questions

The claim that "on warm summer days, residents of the North End can still smell molasses" is frequently repeated and is almost certainly apocryphal — structural engineers and chemists note that any residual molasses would have been washed away or degraded within years. The story persists nonetheless, becoming part of Boston neighborhood lore.

• The tank site is now a recreational park and the location of a small historical marker
• The disaster is covered in the 2003 book Dark Tide by Stephen Puleo, the most comprehensive account written
• Scientific analysis of the tank failure was published in a 2016 paper in the Journal of Chemical Education
• The event predates modern industrial safety regulations by decades

The Great Molasses Flood sits at an unusual intersection of industrial history, corporate negligence, and Boston lore — a reminder that the cost of ignored safety warnings is rarely abstract.