Kenneth T. Jackson writes:
Decoration Day, later designated Memorial Day, began on May 5, 1866, when the small town of Waterloo in Seneca County, New York, organized an entire day of remembrance for its lost sons [of the Civil War]. The idea caught on, and exactly two years later, on May 5, 1868, Major General John A. Logan, commander in chief of the Grand Army of the Republic, the organization of Union Army veterans, issued General Order No. 11, designating May 30, 1868, “for the purpose of strewing with flowers or otherwise decorating the graves of comrades who died in defense of their country.” Logan added that he inaugurated the observance “with the hope that it will be kept up from year to year, while a survivor of the war remains to honor the memory of his departed comrades.”
By 1890, all of the Northern states recognized May 30 as a special day to remember their fallen heroes…After World War I, however, virtually the entire United States accepted Memorial Day (later designated as the last Monday in May) as the primary occasion to remember all those who had died in battle.
“…for which they gave the last full measure of devotion; that we here highly resolve that these dead shall not have died in vain; that this nation, under God, shall have a new birth of freedom, and that government of the people, by the people, for the people shall not perish from the earth.” – Abraham Lincoln, Gettysburg, Pennsylvania, 1863