
United States: historical total unemployment and unemployment rate 1890-1988
However, the longest and most-severe period of mass unemployment in U.S. history came during the Great Depression - unemployment rose from just 3.2 percent in 1929 to one quarter of the total workforce in 1933, and it was not until the Second World War until it fell below five percent once more. Since this time, unemployment has never exceeded 10 percent, although it did come close during the recessions of the 1970s and 1980s.
More recent unemployment statistics for the U.S. can be found here.