The 19th of May, 1780, was distinguished by the phenomenon of a remarkable darkness over all the northern States, and is still called the Dark day.

The darkness commenced between the hours of 10 and 11 A. M., and continued to the middle of the next night. It was occasioned by a thick vapour or cloud, tinged with a yellow color, or faint red, and a thin coat of dust was deposited on white substances.

The wind was in the southwest ; and the darkness appeared to come on with clouds in that direction. Its extent was from Falmouth (Maine) to New Jersey. The darkness appears to have been the greatest in the county of Essex (Mass.) in the lower part of New Hampshire, and Maine; it was also great in Rhode Island and Connecticut. In most parts of the country where the darkness prevailed, it was so great, that persons were unable to read common print, determine the time of day by their clocks or watches, dine, or manage their domestic business, without additional light;  candles were lighted up in their houses; the birds having sung their evening songs, disappeared and became silent; the fowls retired to roost; the cocks were crowing all around as at break of day; objects could be distinguished but a very little distance; and every thing bore the appearance and gloom of night.

—John Warner Barber: Interesting Events in the History of the United States: Being a Selection of the Most Important and Interesting Events which Have Transpired Since the Discovery of this Country to the Present Time. Carefully Selected from the Most Approved Authorities (1828)

The 19th of May, 1780, was a very dark day. Candles were lighted in many houses; the birds were silent and disappeared; and the fowls retired to roost. At this time the Legislature of Connecticut was in session in Hartford. A very general opinion prevailed, that the day of judgment was at hand. The house of Representatives, being unable to transact their business, adjourned. A proposal to adjourn the Council was under consideration. When the opinion of Col. Davenport was asked, he answered, “I am against an adjournment. The day of judgment is either approaching, or it is not. If it is not, there is no cause for an adjournment; if it is, I choose to be found doing my duty. I wish therefore that candles may be brought.”

—Timothy Dwight: Travels in New-England and New-York, Vol. 3 (1822)

It thunderd early this Morning and raind about 7 or 8. About 9 a Darkness came on gradually encreasing at 11. I could neither read nor write without a Candle which soon became necessary for Family Business and continued untill past 3 P.M. A Heavy black Cloud hung at the Westward and Northward, a Thin Vapour Smoak or Fog rising up now and then and almost covering it at Times streaming like the Corruscations of the Aurora Borealis. In the Southern Hemisphere the Clouds appear low, thin and empty running in different Directions. Very little Wind or Rain during the Darkness. The Clouds have a brassy Appearance and the whole Complexion of the Clouds impresses the Mind with an Idea of an Approaching Hurricane, and a universal Gloom everywhere appears. About half after 3 the Wind which before had been South and So. West, sprung up at the North West, dispersd the Clouds and brought us Day. In the Evening the Wind Shifted to the East about 9. at Night and Darkness came on and held untill 12. The Moon had then risen and was full. I frequently during that Time went out of my House and could not abroad discern my Hand tho applied ever so near my Eyes. During the Darkness of the Day, a disagreable Smell was perceivd, some resembling it to the smell proceeding from a Chimney on Fire, others to that which arises from Swamps on Fire. A like Smell was perceivd In the Evening united with that of Sea Salts.

—Letter from Cotton Tufts to John Adams, 19 May 1780 (source)

Image: Illustration from Richard Miller Devens and Charles W. Chase’s The Glory of Our Youth as Portrayed in the Events and Movements that Have Chiefly Distinguished the Marvelous Advance of the American Nation from Colony to World Power (1909)