On January 15, 1919, the North End of Boston was engulfed by a 25-foot-high wave of fermenting molasses traveling at 35 miles per hour. While popular memory focuses on the surreal imagery of streets slick with syrup, the disaster was fundamentally an industrial and logistical failure. The Purity Distilling Company had constructed the massive 50-foot-tall storage tank directly adjacent to the Boston Elevated Railway and harbor freight yards to streamline the transfer of molasses to and from industrial tank cars.
Industrial alcohol derived from molasses was crucial for armaments during World War I, and with Prohibition fast approaching, the company rushed to distill as much alcohol as possible. To meet aggressive rail freight dispatch schedules, the company repeatedly overfilled the tank despite visible leaks and groaning metal walls. Just days before the catastrophe, a massive delivery arrived, filling the tank to capacity.
The rapid influx of cold molasses mixed with older fermenting liquid, creating carbon dioxide gas. Combined with a sudden Boston temperature jump from 2 to 40 degrees Fahrenheit, the pressure inside the under-engineered steel structure surged. When the tank violently disintegrated, the blast destroyed nearby freight cars, lifted an elevated train off its tracks, and killed 21 people while injuring 150.
The disaster triggered a landmark 6-year legal battle that laid the foundation for modern corporate safety regulations.