The Stock Market Crash began the Great Depression. It was not the cause of the Depression but it marked its beginning.
In 1928, the first signs of trouble appeared in the American economy. Consumer demand began to lag somewhat, and this caused cutbacks in the auto and ancillary industries. Speculation on the stock and bond markets continued to grow, even when some of the securities sold had no underlying value.
On the morning of October 24, after a week of falling prices, suddenly millions of shares went on sale. Buy orders did not match these shares. An effort was made by the major Wall Street banks, led by the House of Morgan, to stabilize prices. This effort lasted until October 29, when it was no longer possible to maintain share prices, and the bubble burst. On that day alone, the market lost $10 million.