On 15 January 1919 the ground near 529 Commercial Street in Boston, Massachusetts began to tremble. At the nearby Purity Distilling Company, a six-story-tall molasses tank grumbled like a massive stomach with indigestion. The tank's monumental cache of molasses was awaiting transfer to a processing plant, where it would be used in the production of sweetener, drinking-liquor, and alcohol-based munitions. Moments after the first distressed groan, a sound reminiscent of machine-gun fire echoed in the streets as the tank's rivets buckled in quick succession. The tank burst in a terrific explosion, throwing massive, ragged chunks of sheet-iron into the surrounding buildings. The Purity offices were flattened by the blast, and a nearby fire station was crushed by a flying section of iron.
Despite the force of the rupture, initial damage was limited to the tank's adjacent buildings. The two-and-a-half million gallon column of molasses, however, caused a considerable catastrophe as it spread itself out into the North End neighborhood.
Bystanders were swept up in the smothering goo--tossed and rolled through the thick sludge. The migrating wave of brown syrup pushed buildings off their foundations and overturned wagons, carts, horses, and motorcars. It broke the girders of an elevated rail track, and tossed a train from its tracks. Within minutes several blocks of Boston's streets were buried in struggling victims, rubble of ruined buildings, assorted wreckage, and 2-3 feet of sweet, tacky goo.
Rescue efforts began immediately, but most who ventured in became mired in the mess and soon required rescuing themselves. Terrified survivors were seen running away from the chaotic scene covered from head to toe in dark brown molasses. The USS Nantucket was anchored at the Playground Pier a few block away, and Lieutenant Commander H. J. Copeland sent over a hundred of his able-bodied sailors to lend assistance. Police officers, military personnel, and Red Cross nurses slogged through the knee-deep syrup all night long, searching for sticky victims.
In all, twenty-one lives were lost in the disaster--mostly due 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 day after the catastrophe, paving the way to the Prohibition.
The exact cause of the explosion was never determined definitively, but it is generally attributed to high pressure and a defects in the tank construction. According to some reports, the Purity Distilling Company had neglected to pressure-test the vessel prior to filling it for the first time; so upon its first load of molasses, the outside of the tank was striped with molasses leaks. Rather than paying for repairs, Purity opted to paint the tank brown. On that fateful day in 1919, pressure increases due to fermentation of the molasses and unseasonably warm temperatures put too much strain on these fractures, causing an energetic rupture.
Although its been almost a century since the flood, they say that on a hot day the streets in some parts of Boston still bleed molasses.