Memorial Day was originally call Decoration Day, a day when graves of soldiers who died in service to our country were decorated with flowers, wreaths and flags. By proclamation of General John A. Logan of the Grand Army of the Republic, an organization of former Union sailors and soldiers, this holiday was first widely observed on May 30, 1868 to commemorate the sacrifices of the Civil War soldiers.
According to the History Channel website:
"It is unclear where exactly this tradition originated; numerous different communities may have independently initiated the memorial gatherings. Nevertheless, in 1966 the federal government declared Waterloo, New York, the official birthplace of Memorial Day. Waterloo—which had first celebrated the day on May 5, 1866—was chosen because it hosted an annual, community-wide event, during which businesses closed and residents decorated the graves of soldiers with flowers and flags."
Check out additional information on their site at http://www.history.com/topics/holidays/memorial-day-history
In addition check out these sites for additional information:
Check out the PBS website - National Memorial Day Concert which features Memorial Day History, Meaning, and Traditions & Activities.
Military.com website's Memorial Day page.
Check out U.S. Memorial Day Organization's site at http://www.usmemorialday.org/