May 19, 1780, is known as “New England's Dark Day”.
240 years ago, on that day, a curious event took place: starting at 10 a.m., darkness began to fall on several areas of New England – that includes the territories of Connecticut, Maine, Massachusetts, New Hampshire and Rhode Island - and Canada, terrorizing the inhabitants. In fact, according to reports, the sky had had a strange color for a few hours already.
The phenomenon, albeit to a lesser extent, was noticed all the way to New York and was even recounted by George Washington, who was in New Jersey. According to the testimonies of the time, the darkness was so deep that people had to stop working and light candles to see anything, and the animals retreated to their shelters for the night; the day was apparently followed by an even darker night, which apparently the moon could not light.
The sun returned to shine again in the morning of the next day.
The first explanations for the phenomenon were, of course, of a religious or supernatural kind: some - like the lawmakers in Connecticut, who were gathered that day - feared that the end of the world had come or, in any case, many thought it was caused by divine intervention.
For many years, a sufficiently convincing explanation was not provided. Recently, several researchers have tried to formulate hypotheses. The answer most likely comes from a 2007 study that reported that in the spring of 1780, a large wildfire broke out in Ontario, Canada, whose smoke would have arrived in New England, causing the phenomenon. It is also possible that smoke from fires in Missouri and Arkansas was added to that first one, which would have aggravated the situation. During those times, however, it was impossible for the inhabitants of the areas affected by the "dark day" to be aware of such fires in real time, a fact which - together with the scarce scientific knowledge - fuelled fear and irrational explanations.
Adwar , Crey, Mysterious 'Day Of Darkness' Plunged New England Into Night At Noon On This Day In 1780, Business Insider, 20 May 2014, https://www.businessinsider.com/darkness-fell-at-noon-on-this-day-in-1780-2014-5?IR=T
Alfred, Randy, May 19, 1780: Darkness at Noon Enshrouds New England, Wired, 19 May 2010, https://www.wired.com/2010/05/0519new-england-dark-day/
de Castella, Tom, What caused the mystery of the Dark Day?, BBC, 18 May 2012, https://www.bbc.com/news/magazine-18097177
McMurry Erin R., Stambaugh Michael C., Guyette Richard P., Dey Daniel C. Fire scars reveal source of New England’s 1780 Dark Day, International Journal of Wildland Fire 16, 266-270, 2007 https://doi.org/10.1071/WF05095