The event that marked the beginning of the Dow Jones Industrial Average's precipitous drop in 1929 was the Stock Market Crash of October. Triggered by rampant speculation, overvaluation of stocks, and economic instability, the crash led to widespread panic as investors frantically sold their shares. The market collapse resulted in significant financial loss and contributed to the onset of the Great Depression. The event highlighted flaws in the financial system and led to major reforms in securities regulation in the years that followed.