New England's Dark Day occurred on May 19, 1780, when an unusual darkening of the daytime sky was observed over the New England states and parts of eastern Canada. The primary cause of the event is believed to have been a combination of smoke from forest fires, a thick fog, and cloud cover. The darkness was so complete that candles were required from noon on. It did not disperse until the middle of the next night.
You will note that this happened before automobiles and at the beginning of the Industrial Revolution. There was no global warming. It was just smoke from forest fires, and fog. It's not "unprecedented", because I just showed you a precedent.