The primary cause of the stock market crash of 1929 was the rampant speculation in the stock market, coupled with economic instability. Following a decade of economic growth during the 1920s, investors engaged in excessive buying on margin, inflating stock prices. Once confidence waned, panic selling ensued, leading to a massive drop in stock prices. The crash marked the onset of the Great Depression, severely impacting the global economy, resulting in widespread unemployment and economic hardship that persisted throughout the 1930s.