Bostonians of yesteryear would never know that Jan. 15, 1919 marked a disaster that would go down in history.

Picture this: it’s 1919. World War I has just ended, Prohibition is coming soon, and it’s lunch time. You’re in the North End neighborhood along the waterfront on Commercial Street, where you could find Copps Hill + Langone Park today.

It would be hard to miss the large storage tank, standing over 50 ft tall (about three stories) and measuring approximately 90 ft in diameter (nearly the length of a football field).

The tank was owned and operated by the Purity Distilling Company, which was known for producing grain alcohol. The storage tank was instrumental in producing the highly profitable beverage, holding the key ingredient — fermented molasses.

It was also used to make munitions and other weapons for the war. When full, the tank could hold 2.5 million gallons, which helped the company make nearly five million gallons of alcohol a year.

Moving molasses isn’t as easy as one might think, especially when you factor in the freezing temperatures Boston is known for in the winter.

The tank had just been refilled on Jan. 12, adding an additional 1.3 million gallons to the already noticeably compromised tank. Rumor has it that rumbling sounds could be heard from the leaky container and sometimes the ground would shake.

FYI — one gallon of molasses weighs 11.5 lbs. So the tank was holding approximately 12,000 tons on the day in question (enough to fill three and a half Olympic swimming pools). The weight + gases from the fermentation combined was what some experts believe caused the following events.

Around 12:30 p.m. on Jan. 15, the tank collapsed, spilling 2.3 million gallons of molasses on to the streets of Boston, which as you probably guessed — caused the Great Molasses Flood of 1919.

The wave of black sludge measured from 15-40 ft high + moved about 35 mph. It caused extensive damage — crushing buildings, damaging vehicles, trapping horses, killing 21 people, and injuring over 150 more.

Help was able to arrive quickly but little could be done to aid the situation due to the hardening syrup. The disaster took weeks to clean up and some say you can still smell molasses on a hot day.

To this day there is still much debate on the cause of the disaster, with experts debating the structure, type of steel, and amount of pressure. The devastating events lead to stricter construction codes being adopted locally and by states across the country.