The historical event that marked the start of the Great Depression in 1929 is the Stock Market Crash. Triggered by a period of rampant speculation and financial excess, the crash on October 29, known as Black Tuesday, resulted in a devastating loss of wealth and economic instability. This event led to widespread bank failures, high unemployment rates, and a significant downturn in global economies. Governments around the world struggled to respond effectively, resulting in socioeconomic hardships. The Great Depression reshaped economic policies and led to the implementation of welfare programs under leaders like Franklin D. Roosevelt.