Boston Molasses Tsunami kills 21

The Boston Molasses Disaster, also known as the Great Molasses Flood and the Great Boston Molasses Tragedy, occurred on January 15, 1919.

It happened in the North End neighborhood of Boston, Massachusetts in the United States. A large molasses storage tank burst, and a wave of molasses rushed through the streets at an estimated 35 mph (56 km/h), killing 21 and injuring 150. 

Here is the aftermath...

Some residents claim that on hot summer days, the area still smells of molasses.