The cost of the Civil War

From Measuring Worth, which provides seven indicators for making comparisons in US dollars between any two years from 1774 to the present (2009):

"The Civil War was one of the most devastating events in the history of the United States. It lasted from 1861 to 1865 and has been estimated to have direct cost about $6.7 billion valued in 1860 dollars. If this number were evaluated in dollars of today using the GDP deflator it would be $139 billion, less that one-fourth of the current Department of Defense budget. This would be inappropriate, as would be using the wage or income indexes. The only measure that makes sense for an expenditure of this size is to use the share of GDP, as the war impacted the output of the entire country. Thus the relative value of $6.7 billion of 1860 would be $22 trillion today, or over 150% of our current GDP.

The $6.7 billion does not take into account that the war disrupted the economy and had an impact of lower production into the future. Some economic historians have estimated this additional, or indirect cost, to be another $7.3 billion measured on 1860 dollars. This means the cost of the war (as a share of the output of the economy) was nearly $46 trillion as measured in current dollars."