The first month of the 1929 Wall Street crash’s famous four-day trading collapse was October.
The critical sequence began with Black Thursday on 24 October 1929 and continued through Black Monday on 28 October and Black Tuesday on 29 October. Those sessions produced exceptionally heavy selling and helped destroy confidence after years of rising U.S. share prices.
The market had already reached a major peak in September 1929. Speculation, buying on margin, uneven economic conditions, and fears about overvalued shares made the market vulnerable. After the October losses, the Dow did not reach its ultimate low until July 1932, when it had fallen roughly 89% from its peak.
The crash did not by itself cause every feature of the Great Depression. Bank failures, deflation, falling production, international debt problems, and policy mistakes deepened and prolonged the economic crisis. October identifies the famous initial collapse, not the entire duration of the downturn.