Boston Molasses Flood of 1919

The Great Boston Molasses Flood of 1919


Twenty one people died on February 15, 1919 on what some call the Boston Molassacre.

Why so much molasses? Quite simply, molasses was the base for most of the sugar consumed in the early 20th century. Processed from cane in the Caribbean Islands, the juices of the boiled liquid would concentrate and could then be shipped without risk of spoiling, stored and then further refined to get different grades of sugar.

In this case was ‘blackstrap’ molasses, (the darker concentrated sludge the result of a third boiling) the type of molasses where most of the sugar has been extracted. It could be used to produce ethanol and this is why it was being stored in this location.

The event entered local folklore and residents claimed for decades afterwards that the area still smelled of molasses on hot summer days.

How did it happen?

From The Boston Post

“The disaster occurred at the Purity Distilling Company facility at 529 Commercial Street near Keany Square. Molasses can be fermented to produce ethanol, the active ingredient in alcoholic beverages and a key component in munitions. Purity used the harborside Commercial Street tank to offload molasses from ships and store it for later transfer by pipeline to the Purity ethanol plant situated between Willow Street and Evereteze Way in Cambridge. The molasses tank stood 50 ft (15 m) tall and 90 ft (27 m) in diameter.”

The cause was most likely thermal expansion and an under designed tank. Before the event it had been cold and on the day of the ‘flood’ the temperature climbed to 40F. The older, colder molasses expanded and ruptured the tank. It's said a 25 foot wave of molasses traveled at 35 mph catching some people off guard. The wave was of sufficient force to drive steel panels of the burst tank against the girders of the adjacent Boston Elevated Railway's Atlantic Avenue structure.

Rescue work was supported by some 116 cadets from the Boston Maritime Academy training nearby on the USS Nantucket in the harbor. The molasses started to harden as the weather turned colder making rescue efforts more difficult.

It took clean up crew weeks to clean up. It took longer to clean the rest of Greater Boston and its suburbs. Rescue workers, cleanup crews, and sight-seers had tracked molasses through the streets and spread it to subway platforms, to the seats inside trains and streetcars, to pay telephone handsets, into homes  and to countless other places. "Everything that a Bostonian touched was sticky."

Stories from local guides say curious onlookers would come from all around, neighboring states and even Canada. Many would get stuck in the molasses and complain despite fair warning. Some say this is when the term ‘tourist trap’ was coined.

You don't hear much about molasses anymore but it is still a key ingredient of Boston Baked Beans.

(sources: Boston Post, wikipedia, Boston Globe, the Guardian, npr)

Image By MLHalsey - Own work, CC BY-SA 3.0,