The 28 October 1929 Wall Street crash day was called Black Monday.
The Dow Jones Industrial Average fell 38.33 points, or 12.82 percent, on 28 October 1929. The following day, 29 October, brought another devastating decline and became known as Black Tuesday. Together, these sessions marked the most dramatic phase of the Wall Street Crash, although prices had already begun weakening earlier in October.
The crash followed a long period of heavy speculation, credit-financed share purchases, and rapidly rising stock prices during the 1920s. When confidence broke, investors rushed to sell. Margin calls forced additional liquidation because many buyers had borrowed money to purchase shares.
The crash did not by itself create every problem of the Great Depression, and historians do not treat it as the sole cause. Banking failures, falling demand, monetary policy, and international economic pressures also mattered. A common mistake is to call 29 October Black Monday; that date is Black Tuesday, while 28 October is Black Monday.