Around 12:30 p.m. on Jan. 15, 1919, a large, poorly maintained tank full of molasses on a warm day burst, sending a huge wave of gooey death rampaging down Commercial Street, drowning or crushing 21 people and several horses and cats as it battered the supports of the el that ran down the street and knocked a neighboring fire station off its foundation.
As with so many other major events in the early and mid-20th century, Leslie Jones was there to chronicle the aftermath.
The Boston City Archives posted this map showing the location of the tank (it's the blue circle near the top):
Boston had long imported molasses to turn it into rum. In World War I, and with the coming of Prohibition, though, the molasses in the tank was meant for production of industrial alcohol.
Steven Puleo's Dark Tide remains the definitive work on the disaster in general and the politics surrounding it in particular.
Leslie Jones photo posted under this Creative Commons license.