Unbelievable But True: The Weekly Deep Dive Into History's Strangest Real Events

On January 15, 1919, a wave of industrial sweetener moved through Boston at an estimated thirty-five miles per hour. Mm-hm. This follows our report last week on the Greek village that officially declared war on storks. Correct. The theme of unbelievable but documented events continues. In this case, the event was the Great Molasses Flood. The source was a single storage tank in Boston's North End, owned by the Purity Distilling Company. And this was a large tank. Fifty feet tall, ninety feet in diameter. It held approximately 2.3 million gallons of crude molasses. What was the purpose of that much molasses in downtown Boston? It was destined for fermentation into industrial alcohol.

United States Industrial Alcohol, the parent company, was a primary supplier of alcohol for munitions manufacturing during World War I. This particular shipment had just arrived from the Caribbean. So it was war material, essentially. It was a component of war material. Shortly after noon on that day, witnesses reported hearing a low rumble, followed by what they described as a roar, or a sound like a machine gun, as the rivets shot out of the tank's steel plates. Then the entire structure failed. All at once. Completely. The failure released the entire volume of molasses in an instant. It formed a wave estimated to be twenty-five feet high at its peak and one hundred and sixty feet wide.

Moving at thirty-five miles per hour. That is the accepted engineering estimate. The wave was powerful enough to knock buildings off their foundations. It buckled the elevated railway tracks of the Boston Elevated Railway, and it picked up a freight train car and threw it partly off the tracks. What was the human toll? The immediate destruction was significant. The wave engulfed everything in its path, including people, horses, and wagons. The official casualty count was twenty-one fatalities and one hundred and fifty injured. The cause of death being... drowning? Not precisely. The substance was 1.4 times as dense as water. The force of the wave itself caused significant blunt-force trauma.

Debris carried within the molasses—pieces of the tank, fragments of buildings—also caused fatal injuries. For those trapped, the problem was the viscosity. It's too thick to swim in. Correct. And the day was unseasonably warm for January, around forty degrees Fahrenheit. But when the molasses met the cold surfaces of the street, it began to cool and thicken rapidly. Rescuers had difficulty reaching victims who were encased in it. Many of the deaths were attributed to asphyxiation. So the rescue effort itself was a challenge. It was. The entire neighborhood was coated in a sticky layer that was, in some places, two to three feet deep. The fire department's high-pressure water hoses were ineffective.

They eventually pumped saltwater from the harbor to wash the molasses from the cobblestone streets into the sewer system. The Boston Harbor reportedly remained brown until summer. Was there an official cause determined for the tank's failure? Yes. A multi-year class-action lawsuit followed, one of the first in Massachusetts history. The investigation found the tank was poorly designed and constructed. The steel was too thin—half the thickness it should have been for a tank of its size. It was just built incorrectly. Fundamentally so. It was also never properly tested. Standard procedure would have been to fill it with water first, but the company filled it directly with molasses.

Furthermore, residents had reported for years that the tank leaked. Rivet holes would weep brown streaks down the side. And the company's response? They painted the tank brown, which camouflaged the leaks. The final trigger for the collapse is believed to have been thermal stress. A new, warmer shipment of molasses had been pumped into the tank, causing the colder molasses already inside to expand. The structure could not withstand the additional pressure. So it was a known problem. It was a documented risk. For decades after the event, residents of the North End claimed that on hot summer days, they could still smell the faint, sweet scent of molasses.