The major event that began on October 24, 1929, leading to the Great Depression is known as Black Thursday, marking the stock market crash in the United States. On this day, stock prices plummeted dramatically as panicked investors sold off millions of shares, leading to widespread financial turmoil. The crash signaled the onset of the Great Depression, a severe worldwide economic downturn that lasted through the 1930s. It resulted in massive unemployment, bank failures, and a significant decline in industrial production. The effects of the Great Depression reshaped economic policies and government interventions, prompting reforms in the financial system.