Yes, this really happened.
The Great Boston Molasses Flood
"In 1919, a 50-foot-high steel tank loomed over Boston's North End. Built by the Purity Distilling Company four years earlier, the tank could hold up to 2.5 million gallons of molasses to be used in the production of rum and industrial alcohol. At 12:40 pm on Wednesday, January 19, 1919, the tank burst, sending a gigantic wave of molasses rushing down Commercial Street through the North End, eventually covering two city blocks. Twenty-one people died in the disaster and 150 were injured."