Key causes of the 1929 Stock Market Crash included excessive speculation, buying on margin, and a lack of regulatory oversight. During the 1920s, a booming economy led many investors to purchase stocks with borrowed money, anticipating continued growth. However, by late 1929, market sentiment shifted, revealing underlying economic weaknesses and overvaluation of stocks. The subsequent panic selling triggered a rapid decline in stock prices, resulting in the loss of billions in wealth and triggering a global economic downturn. This crash played a crucial role in the onset of the Great Depression, impacting millions worldwide.