The Molasses Flood of 1919 wreaked havoc on Boston's North End neighborhood, killing 21 people. In January of 1919, a tank containing two million gallons of molasses burst open, unleashing a sticky flood onto Boston's North End. The Great Boston Molasses Flood of 1919 of SEE ALL BACK TO SLIDE. The higher temperature may have helped the molasses spread over the Boston waterfront at such an alarming pace. The researchers also built their own mini molasses flood inside a walk-in refrigerator.