Causes of the Great Depression The main cause of the Great Depression was a lack of understanding of economic systems. The Great Depression began in 1929, during Republican President Hoover’s watch. Many try to blame the worsening of the Depression on Hoover, for his deviation from Republican economic ideology. However, almost all of Hoover's government action occurred during his last year in office, long after the worst of the Depression had hit. In fact, he was voted out of office for doing not doing enough. The economy was turning downward before Hoover took office in 1929. Entire portions of the economy were depressed throughout the 1920’s, such as agricult