On the afternoon of January 15, 1919, people working along Commercial Street in Boston’s North End heard a sound some later compared to machine-gun fire. Rivets were popping out of the steel seams of a huge storage tank by the harbor. Seconds later the tank split apart, and more than two million gallons of molasses poured into the neighborhood. The disaster sounds almost comic today, and people still joke about it. The people who lived through it did not find it funny. Twenty-one people died and about 150 were injured. Buildings were flattened, and for years afterward Bostonians said the waterfront smelled sweet on hot days. It also ended up changing how American cities regulated large structures.
A Tank Built for Wartime Demand
The tank belonged to the Purity Distilling Company, a subsidiary of United States Industrial Alcohol (USIA). Molasses from the Caribbean was the raw material for industrial alcohol, which went into munitions as well as spirits. During the First World War demand surged, and in 1915 the company put up a storage tank about 50 feet high and 90 feet across on Commercial Street, opposite Copp’s Hill. It could hold roughly 2.3 to 2.5 million gallons.
Testimony gathered later suggests the tank was built in a hurry and never properly tested. Neighbors said it leaked from the start and groaned and rumbled as it filled. Children in the mostly Italian immigrant neighborhood collected the drips in cans. According to later court testimony, the company’s answer to the leaks was to paint the tank brown so they showed less. Nobody with structural engineering training had signed off on the design. Massachusetts law did not yet require that.
Twelve-Thirty on a Mild Winter Day
The day the tank failed was unusually warm for a Boston January, after a stretch of bitter cold. A fresh cargo of molasses had arrived from the Caribbean two days earlier to top up the tank, and it had not yet cooled to the outside temperature. Shortly after half past noon, with many workers on their lunch break, the steel gave way.
Estimates of the wave’s height range from about 15 feet to more than 25 feet. Physicists who later reconstructed the event put the leading surge at around 25 feet, moving at roughly 35 miles per hour. It knocked a freight car off its tracks, buckled the steel supports of the Atlantic Avenue elevated railway, and crushed a fire station and several wooden houses. Horses, carts and people were swept off their feet. Many victims were not killed by the impact. They were trapped in the thick liquid and suffocated. The youngest victims were children. The oldest were city workers and teamsters who had been going about their jobs on the waterfront.
Why Rescue Was So Difficult
Rescuers arrived within minutes: sailors from a navy training ship moored nearby, police, firefighters and Red Cross volunteers. They found a scene unlike any ordinary flood. Water drains away. Molasses stays, and it stiffens as it cools. Rescuers waded waist-deep, and some of them got stuck themselves. It took days to recover all of the dead. Some bodies were not found until months later in the harbor.
In 2016 a team of fluid-dynamics researchers at Harvard, including graduate student Jordan Kennedy and engineer Nicole Sharp, ran laboratory tests on molasses to explain what happened. They presented the results at an American Physical Society meeting. Molasses becomes dramatically thicker as its temperature drops. Cooling it from about 10°C to 0°C roughly triples its viscosity. The slightly warm molasses would have surged out fast. Then, as it spread thin on the freezing streets after sunset, it set into something close to a trap. That helps explain why a wave of syrup could be so deadly and why getting people out was such slow work.
Cleaning Up a Sticky City
The clean-up took weeks. Crews used salt water from fireboats to cut through the molasses, then scraped and shoveled the residue. Contemporary accounts say the harbor ran brown for months. Molasses tracked by rescuers, onlookers and carriages ended up on streetcar seats, on telephones and in homes across the city. Many longtime residents said the smell lingered on summer days for decades. That memory is hard to verify, but it is a strong part of the local folklore.
A Landmark Legal Battle
USIA denied that it had done anything wrong. The company argued the tank had been blown up by “evilly disposed persons.” This was a reference to the anarchist bombings that were alarming American authorities in 1919, and the claim was not absurd on its face. Political violence was real that year. But the company never produced convincing evidence of a bomb.
More than a hundred lawsuits were combined into one of the first major class-action style cases in Massachusetts history. The court appointed an auditor, Hugh Ogden, to hear the evidence. Over several years he listened to thousands of pages of testimony from engineers, metallurgists, survivors and company officials. Expert witnesses pointed to steel that was too thin for the load, too few rivets, and the lack of any proper load test before the tank was filled. In 1925 Ogden concluded that the tank had been structurally unsound and that USIA was responsible. The company paid substantial damages to victims and their families, reported at several hundred thousand dollars, a very large sum for the time.
A Lasting Legacy in Building Codes
The verdict mattered beyond Boston. It came at a time when large industrial structures could be put up with very little public oversight. After the flood, Massachusetts and then other states tightened their rules. They required that plans for major structures be reviewed and signed by qualified engineers and architects, and that calculations be filed with building authorities. These requirements are now standard, which makes it easy to forget that some of them were written in response to a disaster involving syrup.
Modern engineering studies have kept looking at the case. Analyses of surviving steel samples and of the design point to several problems: steel that was more brittle than ideal in cold weather, walls too thin for the pressure at the base, and stress concentrated around the rivet holes. Researchers differ on how much weight each factor deserves, but none of the modern studies supports the sabotage theory.
Remembering the Victims
Today the site is part of Langone Park, with ball fields and a waterfront view. A small plaque recalls the disaster and lists those who died. For years the flood was mostly remembered as a curiosity, partly because its timing was overshadowed by the end of the First World War, the flu pandemic and the ratification of Prohibition that same week. Historians and local writers, most notably Stephen Puleo in his book Dark Tide, have since brought back the human side of the story. Most of the victims were working-class Bostonians: laborers, a city paving worker, firemen and children collecting firewood. Their deaths showed that a company could get away with cutting corners when nobody was checking.
The Great Molasses Flood is still a favorite piece of odd trivia, but it also explains part of how modern cities protect themselves. It showed that industrial risk was a public concern, that engineering decisions needed to be checked, and that corporations could be held to account in court. The next time you see an engineer’s stamp on a building permit, part of the reason it is there goes back to a warm January afternoon on Commercial Street in 1919.
Sources
- Britannica: Great Molasses Flood
- ScienceDaily (American Physical Society): Sweet but deadly 1919 disaster explained
- HISTORY: The Great Molasses Flood of 1919
Featured image: BPL / Wikimedia Commons, Public domain
