What was the Great Boston Molasses Flood of 1919?

The Great Molasses Flood, also called the Boston Molasses Disaster, happened on January 15, 1919, in the North End neighborhood of Boston. A large storage tank holding about 2.3 million gallons of molasses burst, and the wave of syrup rushed through the streets at an estimated 35 miles per hour. It killed 21 people and injured 150. [1]

The steel tank stood 50 feet tall and about 90 feet across, on Commercial Street. According to History.com, it belonged to United States Industrial Alcohol, which used Caribbean molasses to make alcohol for liquor and munitions. The tank was built in 1915 as World War I raised demand, and the construction was rushed. Boston.gov says it was built by Purity Distilling Company, and the two accounts differ on how the ownership is described. [1] [2] [3]

Residents knew the tank leaked. Boston.gov, citing the author Stephen Puleo, reports that children collected molasses from the seams and that the company painted the tank brown to hide the seepage. History.com adds that at least one employee warned managers it was unsound, but the company mostly just re-caulked it. [3] [2]

Temperatures had climbed above 40 degrees Fahrenheit after a frigid stretch, and a ship had delivered a fresh, warmed load of molasses the day before. The tank failed at around 12:30 p.m., though sources give times from 12:30 to about 1 p.m. Witnesses described a roar like an elevated train, and rivets shot out with a sound many compared to machine-gun fire. [1] [4] [3]

Scientific American describes a wave about 7.5 meters high at its peak. It crushed freight cars, tore a firehouse from its foundation and nearly lifted an elevated train off its tracks. Molasses is a non-Newtonian fluid: it surged fast enough to demolish buildings, then settled into a thicker state that trapped people. About half the victims died that day, and the rest died of injuries and infections in the following weeks. [5]

Several factors are cited rather than a single cause. These include thin walls, a metal prone to cracking, poor testing, rapid temperature change, and possibly carbon dioxide from fermentation raising the pressure inside. A fatigue crack near a manhole cover may have grown until it failed. The company first blamed an anarchist bomb plot, but an inquiry and a class-action lawsuit exposed the tank's weaknesses. In 1925 a court-appointed auditor ruled that the owners' negligence was to blame. [1] [5] [3]

Puleo argues the disaster helped drive rules requiring engineers to sign and seal plans and building inspectors to review projects. After a two-week cleanup, residents reported for decades that the area still smelled of molasses on hot summer days. [3] [1]