On May 5, 1866, the village of Waterloo, New York was decorated with flags at half mast, draped with evergreens and mourning black, and flowers were placed on the graves of those killed in the Civil War. In the following years, the ceremonies were repeated.
Later, Maj. Gen. John A. Logan, Commander-in-Chief of the Grand Army of the Republic, declared that “Decoration Day” should be observed on May 30. It is believed that date was chosen because flowers would be in bloom all over the country.
“The 30th day 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.” (General Order 11)
The first large observance was held that year at Arlington National Cemetery, across the Potomac River from Washington, DC.
By the end of the 19th century, Decoration Day ceremonies were being held on May 30 throughout the nation. State legislatures passed proclamations designating the day, and the Army and Navy adopted regulations for proper observance at their facilities.
In May 1966, Congress unanimously passed a resolution and President Lyndon B Johnson signed a Presidential Proclamation recognizing Waterloo as the Birthplace of Decoration Day / Memorial Day.
It was not until after World War I, however, that the day was expanded to honor those who have died in all American wars.
In 1971, Memorial Day was declared a national holiday by an act of Congress, though it is still often called Decoration Day. It was then also placed on the last Monday in May.