The following chart shows the public debt (in 2009 dollars) from 1940 through the estimated 2009. The debt rose rapidly during the 1980s due to large federal deficits. The rise slowed dramatically in the 1990s and the debt even began to decline at the end of the decade. The debt sharply rose after 2001 due again to large deficits.
Source: Office of Management and Budget, Budget of the U.S. Government, FY2009, Historical Tables [1].
Links:
[1] http://www.whitehouse.gov/omb/budget