Boston's Great Molasses Flood

On a warm January day in Boston, a giant brown wave raced through the streets destroying everything in its path. A 2,300,000-gallon tank of molasses at the Purity Distilling Company's facility had unexpectedly burst killing 21 people and injuring 150 more. The tank exploded with such force that the rivets holding the panels shot out like machine gunfire and buildings were flattened. To this day, residents of the community still claim to be able to smell molasses on warm days.

The Day of the Accident

On January 15, 1919 it was an unseasonably warm 46° F in Boston. These days molasses is a rarely used ingredient, but at the beginning of the century it was the most common sweetener in the United States. It could also be distilled to produce rum and ethyl alcohol. The ethyl alcohol was an important element in the creation of the explosive component of ammunition at that time.

The 50ft high by 90ft diameter molasses storage tank at Purity Distilling Co. had been filled to capacity. This had only been done a handful of times in the past and put the tank under enormous stress. The exact cause of the accident was never determined but several factors most likely contributed to the collapse. The unusually warm weather most likely started the fermentation of the molasses unexpectedly. The process would have created carbon dioxide gas that had nowhere to escape to and increased the pressure within the tank.

The tank had also been poorly constructed and suffered problems from the start. Standard practice was to fill tanks of this kind with water to test for leaks but this was never done. When the tank was filled with molasses the tank leaked so much the company had to paint it brown to hide the molasses seeping out. Local residents would even scrounge the seeping molasses from the side of the tank for their own use.

When the tank finally gave way, a witness described the experience like the feeling of a train passing by. A loud rumble combined with the sound of a machine gun as the rivets flew out of the tank’s ½ inch steel panels. The panels flew off with such force that they cut the girders of a nearby elevated train track and flattened the neighboring fire station.

The wave of molasses was described as between 8 and 15 feet high and moved at 35 mph and with enough force to knock buildings off their foundations and push automobiles down the streets. When it retreated the vacuum it formed was enough to suck a truck back towards the tank. When the molasses settled, it flooded several blocks with 2 to 3 feet of the sticky goo.

21 people were killed either by drowning or being crushed in the debris, and another 150 were injured. Fortunately a US Navy training ship was docked nearby and 116 cadets rushed to the scene. Rescuers were hampered by the sticky brown goo and temperatures that soon began to fall. After 4 days of looking the searchers abandoned their efforts. The victims were so covered in molasses that identifying them was difficult, and the final couple of victims to be found couldn't be identified at all.

The Aftermath

A lawyer for the Purity Distilling Co. rushed to the scene within hours of the accident. He claimed that the accident was actually the result of sabotaging by anarchists because some of the molasses was destined to be distilled into alcohol for use in ammunitions. Ultimately this theory was thrown out, and it was found that an access hatch at the base of the tank had a crack that grew until it catastrophically failed.

In the first class action lawsuit in the state, residents sued Purity Distilling Co.’s parent company, United States Industrial Alcohol Company. They were eventually awarded a total of $600,000 (approximately $7 million in today’s dollars) in out of court settlements.

Cleaning the mess took almost 6 months and the harbor was still brown by summer. Today, the original site of the tank is owned by the city and is home to a public baseball field.

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