Memorial Day, originally called Decoration Day, is a day of remembrance for those who have died in service of the United States of America. 
Memorial Day was borne out of the Civil War and a desire to honor our dead.  It was officially proclaimed on 5 May 1868 by General John Logan, national commander of the Grand Army of the Republic, in his General Order No. 11.  “The 30th of May, 1868, is designated for the purpose of strewing with flowers, or otherwise decorating the graves of comrades who died in defense of their country during the late rebellion, and whose bodies now lie in almost every city, village and hamlet churchyard in the land,” he proclaimed.  The date of Decoration Day, as he called it, was chosen because it wasn’t the anniversary of any particular battle.
(from usmemorialday.org)

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