History: The Great Depression, 1939-1943, United States

Start of the Great Depression
Economic historians usually attribute the start of the Great Depression to the sudden devastating collapse of US stock market prices on October 29, 1929, known as Black Tuesday; some dispute this conclusion, and see the stock crash as a symptom, rather than a cause, of the Great Depression.
Even after the Wall Street Crash of 1929, optimism persisted for some time; John D. Rockefeller said that "These are days when many are discouraged. In the 93 years of my life, depressions have come and gone. Prosperity has always returned and will again." The stock market turned upward in early 1930, returning to early 1929 levels by April. This was still almost 30% below the peak of September 1929.