Great Depression in the United States - Wikipedia

The Great Depression was the greatest and longest economic recession of the 20th century and, by some accounts, modern world history. By most contemporary accounts, it began with the U.S. stock market crash of 1929, and didn't completely end until after World War II, in 1946. Economists and historians often cite the Great Depression as the most critical economic event of the 20th century.

The NYSE bubble burst violently on Oct. 24th, 1929, a day that came to be known as Black Thursday . The following week brought Black Monday (Oct. 28) and Black Tuesday (Oct. 29); the DJIA fell more than 20% over those two days. The stock market would eventually fall almost 90% from its 1929 peak.

Ripples from the crash spread across the Atlantic Ocean to Europe, triggering other financial crises; with the collapse of the Boden-Kredit Anstalt, Austria’s most important bank, in 1931, the economic calamity hit the Continent in full force.