On January 15, 1919, a sound later described as a dull, muffled roar emanated briefly from the six-story-tall molasses tank at the Purity Distilling Company. This grumbling was heard for only a moment, when it was shortly interrupted by a terrific explosion that sent the tank's half-inch-thick sheet iron shell flying through the air in three giant pieces. The force of the explosion demolished several nearby buildings, including a fire station which was crushed by a huge chunk of the steel tank, and the Purity offices which were flattened.
Even more catastrophically, the tank's two-and-a-half million gallons of molasses were loosed upon the city. A huge wave of molasses flowed swiftly down the surrounding streets, pushing buildings off their foundations and overturning wagons, carts, horses, and motorcars. It broke the girders of a nearby elevated train, and tossed a train from its tracks. The streets were quickly filled with the sticky debris of ruined buildings, and syrupy molasses sludge up to three feet deep.
Rescue efforts began immediately, but most who ventured into the mess quickly became mired in the goo, and soon required rescuing themselves. Terrified survivors were seen running away from the chaotic scene covered from head to toe in dark brown molasses.
In all, twenty-one lives were lost in the disaster-- mostly to crushing and asphyxiation-- and 150 injuries were reported. It is said that a lawyer for Purity arrived on the scene within hours and tried to pin the disaster on anarchist saboteurs, but despite this continued insistence, the company ultimately paid out about $1 million in settlements, equivalent to about $11 million today. The nearby harbor remained brown through the rest of the winter and spring, and it took over six months to clean the structures, automobiles, and cobblestone streets of the sticky mess.
By coincidence, the 18th amendment of the US Constitution was ratified the very next day, enabling the Prohibition.