Origins and history
More than a half dozen places have claimed to be the birthplace of the holiday. In October 1864, for instance, three women in Boalsburg, Pennsylvania, are said to have decorated the graves of loved ones who died during the Civil War; they then returned in July 1865 accompanied by many of their fellow citizens for a more general commemoration. A large observance, primarily involving African Americans, took place in May 1865 in Charleston, South Carolina. Columbus, Mississippi, held a formal observance for both Union and Confederate dead in 1866. By congressional proclamation in 1966, Waterloo, New York, was cited as the birthplace, also in 1866, of the observance. In 1868 John A. Logan, the commander in chief of the Grand Army of the Republic, an organization of Union veterans, promoted a national holiday on May 30 “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.”
After World War I, as the day came to be observed in honor of those who had died in all U.S. wars, its name changed from Decoration Day to Memorial Day. Since 1971 Memorial Day has been observed on the last Monday in May. A number of Southern states also observe a separate day to honor the Confederate dead. Information courtesy of Encyclopedia Britanica – Memorial Day | Weekend, Meaning, Facts, & History | Britannica