The 1929 U.S. market crash day on which the Dow Jones fell nearly 13 percent on October 28 was Black Monday.
On October 28, 1929, the Dow Jones Industrial Average fell 38.33 points, or 12.82 percent. The next day, Black Tuesday, brought another enormous decline as panic selling continued. Together, the two sessions became defining moments of the Wall Street Crash of 1929.
The market had risen rapidly during the 1920s, supported by widespread speculation and buying shares with borrowed money. When confidence broke, forced selling and shrinking credit intensified the decline. The crash contributed to the broader economic collapse known as the Great Depression, although it did not by itself cause every feature of that depression.
Black Monday here refers specifically to October 28, 1929. It should not be confused with the better-known 1987 Black Monday, which occurred nearly six decades later.