On October 24, 1929, known as Black Thursday, the U.S. stock market crashed, marking the beginning of the Great Depression. The crash began after weeks of stock prices becoming inflated and unsustainable, leading to mass panic selling. More than 12.9 million shares were traded in a single day, and the market lost billions in value. The event led to widespread financial instability and unemployment across the United States, plunging the country into the Great Depression. The crash prompted the introduction of significant reforms in U.S. financial systems to prevent future collapses.