The Great Depression
From Dickinson College Wiki
From 1929 to 1933, real output fell by about 30%.
From 1929 to 1933, unemployment rose from about 3% to about 25%.
From 1929 to 1933, the dollar deflated on average 10% per year.
From 1929 to 1933, the money supply fell by about 30%.
To put this in perspective we can look at another deflationary episode in American history.
From 1973 to 1975, real output fell by about 3.4%.
From 1973 to 1975, unemployment rose from around 4% to 9%.