“Great Myths of The Great Depression”- Lawrence W. Reed. The Great Depression started in the United States back in 1930s all through the 1940s. This depression was one of the greatest economic in U.S history. You had millions and millions of people who were jobless or soon to be jobless. What were the causes of The Great Depression what caused millions of people to lose their job. Although there were several factors that came together to cause the Great Depression, the three main reasons were the business cycle, the overproduction, and the saving/Investing. The first main cause of the Great Depression was the Business Cycle. The Business Cycle has a four stage which is Expansion Peak contraction and trough. In business cycle/ stock market