It sounds like a joke — but it really happened.

On a chilly January day in 1919, a massive storage tank in Boston burst, unleashing more than 2.3 million gallons of molasses into the city streets. The sticky wave was reportedly moving at 35 mph (56 km/h) and stood over 25 feet (7.6 meters) high.

Buildings were crushed. Horses were swept away. People were literally trapped in syrup. In total, 21 people died and over 150 were injured. Rescuers described the scene as “like walking through glue.”

Cleanup took weeks. Some say the smell of molasses lingered in Boston for decades.

Why did it happen? The tank had been poorly built, rarely inspected, and overloaded. When it collapsed, it turned a sweet treat into one of the strangest disasters in U.S. history.

To this day, locals refer to it as the Great Molasses Flood — a bizarre, sticky reminder that even sugar can be deadly.