A Strange Disaster: Great Molasses Flood of 1919

It’s been over 100 years, but people are still talking about the Great Molasses Flood that struck Boston on January 15, 1919. This tragedy is one that almost seems made up. But it’s a true tale—a tsunami of molasses let loose on the city that caused devastating loss of life and damage to property. How did such a crazy thing happen?

The Great Molasses Flood: Before and After

All seemed well in Boston’s North End but little did anyone know that a gigantic molasses tank operated by the Purity Distilling Company was about to spark a disaster. This tank was massive, standing 50 feet high and 90 feet in diameter. It was designed to hold 2.5 million gallons of molasses, which was enough to fill 3 1/2 Olympic-sized swimming pools, and it was made from steel, a little more than half an inch thick.

While people living and working in the area suspected nothing, there were a few warning signs that disaster was imminent. The tank leaked—and it had leaked for a long time, enough that local neighborhood children knew to bring empty cups and cans to the tank to collect the free molasses that dripped from it. In fact, employees had been concerned that it was a safety hazard, but instead of making repairs, the tank’s owners simply painted the tank the same color as molasses to help hide the leaks. And there were other signs, like ominous creaks and groans whenever new molasses was added to the tank.

People in the area reported hearing a few loud sounds—like machine-gun fire—as the tank’s rivets began popping loose. The tank exploded and set free a tidal wave of molasses that measured between 15 and 25 feet at its highest, and about 165 feet wide. The destructive tide, about 2.3 million gallons of molasses in all, pounded through the neighborhood reaching a maximum speed of 35 MPH.

The Aftermath

The damage was catastrophic. When all was said and done, the molasses flood claimed the lives of 21 people, ages ranging between 10 and 78. Two ten-year-old children collecting firewood nearby were swept away by the tide, and some city workers who were outside eating lunch at the time drowned in the flood. Another man, Martin Clougherty, told the Boston Globe in an interview that he was sleeping in his home and woke to find himself in several feet of molasses. About 150 people were injured. The flood trapped animals, too, resulting in the deaths of at least 25 horses.

The flood demolished homes and other buildings as it swept into the Boston Harbor. It also knocked a truck through a fence, damaged a railway, and pushed the local firehouse off its foundation. By today’s reckoning, the flood caused about $100 million in damages.

Rescue Efforts Proved Difficult

The wave itself was just the beginning. Firemen and police officers spent four days wading through waist-deep molasses to rescue people. Worse, the molasses behaved a lot like quicksand. Because molasses is thick and syrupy, new challenges arose as temperatures started to drop. When the spill occurred, temperatures were about 40 degrees, but as night fell, the molasses all over Boston’s North End cooled and thickened, firmly trapping anyone who hadn’t already been rescued. Some experts say that rescue efforts likely would have been much easier if the spill had happened in the height of summer rather than the dead of winter because the molasses wouldn’t have thickened so much.

And then there was the cleanup. All in all, the cleanup took about 80,000 hours of labor. Firefighters at first attempted to wash the molasses away with their hoses, but water proved ineffective—though they discovered that saltwater was more effective at “cutting” the molasses than freshwater, so millions of gallons were pumped in. Cleanup efforts took so long that it was months before the last of the bodies were found. Some have reported that even decades after the cleanup was complete, Boston’s North End still smelled of molasses, particularly on warm days.

What Went Wrong?

Investigations and accusations swirled around the Great Boston Molasses Flood. The company that owned Purity Distilling Company—the U.S. Industrial Alcohol Corporation—said that the disaster was caused by anarchists, who had sabotaged the tank with explosives. In those days, this wasn’t an entirely implausible explanation. Anarchists were known for such things, and in fact, 40 explosions linked to anarchists had been reported in Boston in the year leading up to the Great Molasses Flood.

But after a five-year court battle, it was ruled that anarchists weren’t to blame—only shoddy construction methods. Officials determined that the disaster was in part caused by a supervisor who lacked the training to read blueprints during the tank’s construction. The USIA had never hired certified engineers or architects to check the tank, and substandard construction materials had been used in the tank’s construction, including steel that was too thin and improperly forged.

The temperature was another factor. In the days prior to the tank’s failure, temperatures shifted from about 2 degrees F to 40 degrees. On top of it, the tank had been topped up with warm molasses, which mixed with the cold molasses inside. The temperature increases caused gas to expand within the tank, which led to its collapse. In the end, USIA was ordered to pay about $15 million dollars in today’s money as damages.

And that’s the story of the Great Boston Molasses Flood, a tragedy that reshaped building regulations nationwide. Today, few are aware of the flood or its significance, but if you ever visit Boston’s North End, you’ll find a green plaque on the side of a building where the tank once stood to commemorate this historic disaster.