Deflation
Deflation occurred periodically in the U.S. during the 19th century (the most important exception was during the Civil War). This deflation was at times caused by technological progress that created significant economic growth, but at other times it was triggered by financial crises — notably the Panic of 1837 which caused deflation through 1844, and the Panic of 1873 which triggered the Long Depression that lasted until 1879. These deflationary periods preceded the establishment of the U.S. Federal Reserve System and its active management of monetary matters. Episodes of deflation have been rare and brief since the Federal Reserve was created (a notable exception being the Great Depression) while U.S. economic progress has been unprecedented.
Farm Security Administration
The Great Depression began in August 1929, when the United States economy first went into an economic recession. Although the country spent two months with declining GDP, it was not until the Wall Street Crash in October 1929 that the effects of a declining economy were felt, and a major worldwide economic downturn ensued. The market crash marked the beginning of a decade of high unemployment, poverty, low profits, deflation, plunging farm incomes, and lost opportunities for economic growth and personal advancement. Although its causes are still uncertain and controversial, the net effect was a sudden and general loss of confidence in the economic future.