The cause of the Great Depression in the early 20th Century is a matter of debate about economic crisis, even though the common belief is that the Great Depression was triggered by the 1929 crash of the stock market. The Great Depression began in October, 1929 on a day now known as Black Tuesday. The Great Depression was the longest lasting economic downturn in history, that is recorded. In the United States, the Great Depression began soon after the stock market crash which sent Wall Street into a panic and wiped out millions of investors. President Franklin D. Roosevelt helped lessen the effects of the Great Depression, the economy would not fully turn around until after 1939. The Great Depression was the worst economic crisis in U.S. history. From 1931 to 1940 unemployment sky rocketed and there became less and less jobs. In April 1939, almost ten years after the crisis began, more than one in five Americans could not find work even after ten years since the end. On the surface World War II seems to mark the end of the Great Depression.