January 15, 1919: A Wave of Sticky Death
At 12:40 pm on an unseasonably warm winter afternoon, a five-story steel tank filled with 2.3 million gallons of molasses burst in Boston's North End. The explosion released a 25-foot wall of thick, dark syrup that thundered through the streets at 35 miles per hour. Buildings collapsed. People were swept away. Horses were trapped. The force of the flood was so intense that it tore the nearby elevated railway structure from its foundation.
The Making of a Disaster
The molasses in question was 2.3 million gallons of industrial-grade blackstrap, a byproduct of Caribbean sugar refining. The tank, owned by United States Industrial Alcohol Company (USIA), stood 58 feet high and 98 feet wide at Commercial and Charter Streets. It had been built in 1915 to hold molasses destined for nearby munitions factories, where the syrup was distilled into industrial alcohol for World War I munitions. The tank was poorly constructed: steel plates were only one-half inch thick instead of the recommended seven-eighths of an inch, and inspiration holes were left unfilled. Workers had reported ominous groaning sounds for months before the disaster, but their warnings were ignored.
Survivors' Stories from the Flood
"It looked like a big black sea" is how Carmen Dicenso remembered the wave. Dicenso was 12 years old in 1919. He watched from a second-floor window as the molasses engulfed the street below. The wave reportedly reached heights of 25 to 30 feet and destroyed everything in its path, including the nearby elevated railway structure, which was torn from its foundation. One firefighter was swept into the harbor, where he floated for hours until rescue boats found him. Another man, who had been working on the railway, was trapped in the molasses for six hours before rescuers could free him. A third survivor, battered and covered in sticky syrup, described the sensation as "like being in quicksand," according to the Boston Globe archives.
The Human Toll
When the disaster was over, 21 people were dead and 150 were injured. Victims ranged from workers at the tank to bystanders. Among the dead was a 10-year-old boy, and a 78-year-old woman who watched the scene from her window. The youngest was a baby who had been in her mother's arms when the wave struck. The Boston Public Library maintains a list of names and ages of all victims, which is consulted for annual remembrance ceremonies.
Why Molasses Behaves Like Water
At room temperature, molasses pours slowly, but on January 15, 1919, the temperature had risen to 43°F from a frigid near-freezing level the previous day. This warming caused thermal expansion within the tank, increasing internal pressure. Engineers at MIT later calculated that the stressed tank burst under the pressure of the warming contents. University of Massachusetts sources note that molasses indeed behaves like water in a wave at a certain temperature range, flowing with similar force despite its viscosity. The key factor is temperature. When warm, molasses flows more readily, creating the wave effect that claimed lives.
Cleanup Challenges
Rescuers couldn't reach many victims quickly due to the sticky syrup. The Boston Fire Department, which had been built only steps from the tank, was among the first responders. The Fire Department hosed down the area and the harbor for weeks. But the molasses refused to wash away easily. It coated the rescue workers themselves, hindering their ability to coordinate efforts. The syrup mixed with seawater and formed a sticky layer that covered the beach and poured into the harbor for months. Even in summer, residents could taste or smell the odor of molasses. The cleanup required not only hoses but scrapers, shovels, and sand as crews worked to remove the sticky, thick substance from buildings, sidewalks, and the beach.
Legal Battles and Class Action Lawsuits
In 1920, USIA argued that the tank had been destroyed by Italian anarchists, claiming that anarchist plots were responsible for a series of bombings in the United States during the war years. The company repeatedly emphasized that the disaster had occurred on the same day as another bombing elsewhere, according to the National Archives. A class action lawsuit followed. Boston attorney Frank Sherman represented relatives of victims. His law office compiled detailed witness statements and technical evidence. In one of the first class-action cases in American history, Sherman successfully argued that the tank's failure resulted from USIA's negligence, not sabotage. The trial was lengthy. Over 3,000 witnesses were called, and the case was settled in 1925 without an appeal. USIA paid $628,000 in damages (equivalent to $8.7 million today), according to inflation calculators at the US Bureau of Labor Statistics.
The Liquid Legacy
The disaster is noted for several engineering firsts. It caused the city to revise building codes, including requirements that industrial tanks meet specific safety standards. The case established legal precedents for corporate liability. It also serves as a cautionary tale for engineers and managers who ignore warning signs. The city of Boston commissioned a report that concluded the tank's failure was due to poor construction and neglect of warnings. This report became a model for similar investigations later. Memorial remembrance ceremonies have been held in the North End in January each year since 2019, the centennial of the disaster.
How the Molasses Flood Changed Engineering
After the disaster, engineers began to seriously consider the properties of liquids in large quantities. The American Society of Civil Engineers created new guidelines for industrial tank construction, including requirements for thicker steel plates, better riveting patterns, and regular structural inspections. The Massachusetts Institute of Technology began offering courses on industrial safety and storage of fluids. The disaster serves as a textbook illustration of how structural failure occurs due to internal pressure, thermal expansion, and neglect of warning signs. Today, civil engineers use finite element analysis to predict stress points in industrial structures, and safety inspectors must receive specialized training in evaluating tanks and storage vessels.
Molasses and Modern Chemistry
Professor Joseph Cecchini at Stevens Institute of Technology points out that molasses is 72% sugar and has a density of 1.43 g/cm³. At 40°F, its viscosity is approximately 5 Pascal-seconds, compared to water's viscosity of 0.001 Pascal-seconds. This difference creates a challenge to model accurately, especially when volume is combined with rapid flow. In studies funded by MIT, researchers showed that molasses at 40°F flowed at a speed of 35 mph, with a Reynolds number of about 10, indicating a laminar flow pattern distinct from water's turbulent flow. These findings helped redesign safety protocols for large-scale storage facilities.
Remembering the Disaster
Today, the former site of the tank has been redeveloped. A baseball field stands where the catastrophe unfolded. A stone marker from 2007 pays tribute to the victims. The marker reads "Molasses Flood Area 1919" and includes a list of names of those who died. Visitors often ask about the odd event, and tour guides are instructed in the history of the disaster. The Boston Public Library holds a trove of photographs, maps, and personal accounts of the flood. Local schools include the flood in history classes, using it to discuss the importance of safety regulations. For the descendants of victims, the site serves as a place of pilgrimage, and families often speak of the disaster during interviews with genealogy researchers.
The Science Behind the Stickiness
Molasses is essentially concentrated sugar water. Sugarcane or sugar beet juice is boiled to produce sugar crystals, and the residual thick liquid is molasses. The syrup is sticky because of hydrogen bonding between sugar and water molecules creates a viscous, non-Newtonian fluid. When agitated, molasses becomes less viscous, a property that explains the surging wave effect during the disaster. The higher density (1.43 g/cm³) made the wave even more forceful than a similar wave of water, as the fluid exerted greater pressure on surrounding structures. Understanding the non-Newtonian properties of sugar solutions has applications in modern industrial design, particularly in confectionery and chemical manufacturing.
Sources and Disclaimer:
This article was generated by SpaceFactsBot. For verification, see the following reputable sources: "The Great Molasses Flood" by the Boston Public Library, "Mass Moments" historical entries from the Massachusetts Historical Society, and the National Archives holdings on industrial accidents.