The non-partisan Congressional Research Service last week published a study (PDF) calculating the cost of every major U.S. war, "from the American Revolution through current conflicts in Iraq, Afghanistan, and elsewhere." (The numbers are all in 2008 dollars.) The study was first flagged -- and posted online -- by Steven Aftergood at the Federation of American Scientist’s Secrecy News.
There's a snapshot on your left. You can also look at the full graphic -- along with the option to view war costs by size of GDP. (We created the graphic using a free Web site from IBM called ManyEyes.)
The report notes that the estimates are likely an undercount: "All estimates are of the costs of military operations only and do not include costs of veterans benefits, interest paid for borrowing money to finance wars, or assistance to allies."