The depression was caused by a number of serious weaknesses in the economy. Although the 1920s appeared on the surface to be a prosperous time, income was unevenly distributed. The wealthy made large profits, but more and more Americans spent more than they earned, and farmers faced low prices and heavy debt. The lingering effects of World War I (1914-1918) caused economic problems in many countries, as Europe struggled to pay war debts and reparations. These problems contributed to the crisis that began the Great Depression: the disastrous U.S. stock market crash of 1929 (see Black Monday), which ruined thousands of investors and destroyed confidence in the economy. Continuing throughout the 1930s, the depression ended in the United States only when massive spending for World War II began.
The depression produced lasting effects on the United States that are still apparent more than half a century after it ended. It led to the election of President Franklin Delano Roosevelt, who created the programs known as the New Deal to overcome the effects of the Great Depression. These programs expanded government intervention into new areas of social and economic concerns and created social-assistance measures on the national level. The Great Depression fundamentally changed the relationship between the government and the people, who came to expect and accept a larger federal role in their lives and the economy.