What was the name of the 1929 Wall Street Crash day when the Dow fell 12.8%?

The 1929 Wall Street Crash day when the Dow fell 12.8% was known as Black Monday.

Black Monday occurred on 28 October 1929, when the Dow Jones Industrial Average lost 38.33 points. The decline followed weeks of nervous trading and came immediately before Black Tuesday, when the Dow fell another 11.7%.

The crash was not caused by one isolated event. Speculative buying, widespread margin debt, slowing economic activity, and weakening confidence all contributed. The market had reached a record high in September 1929 before its dramatic reversal.

Black Monday and Black Tuesday are sometimes treated as one event, but they were separate trading days. The crash continued afterward, and the Dow ultimately reached its low in July 1932, losing nearly 89% from its 1929 peak.