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.
Wall Street Crash of 1929
The American mobilization for World War II at the end of 1941 moved approximately ten million people out of the civilian labor force and into the war. World War II had a dramatic effect on many parts of the economy, and may have hastened the end of the Great Depression in the United States. Government-financed capital spending accounted for only 5 percent of the annual U.S. investment in industrial capital in 1940; by 1943, the government accounted for 67 percent of U.S. capital investment.