Memorial Day isn’t just about barbecues and traffic jams. Originally known as Decoration Day, this federal holiday began after the Civil War to commemorate the Union and Confederate soldiers who died in the war. Memorial Day now honors all Americans who have died in military service.

In 2010, the Congressional Research Service published a report on war casualty statistics, in response to numerous requests for data. Compiled from sources at the Department of Defense, it indicates the number of casualties among American military personnel serving in principal wars and combat actions. Data before World War I are based on incomplete records in many cases. Casualty statistics for wars long ended, such as Vietnam and Korea, are updated periodically, usually when remains are identified and persons previously listed as missing in action are reclassified as dead.