As a retired Army officer, I tend to get pretty exercised at the widespread notion in the media and public commemorations of Memorial Day that this day is set aside to honor living veterans. It's not. That's done on Nov. 11, Veterans Day.
Memorial Day is to honor and give thanks for the service, dedication and sacrifice of members of the American armed forces who gave their lives in the service of their country. We also honor those who survived their service but have died since.
Which is to say that Memorial Day is set aside to honor the memory of dead, not thank the living.
Memorial Day as we know it grew from diverse strands of decorating the graves of Civil War dead, begun in various towns just after the war ended. One tradition says that Southern women, mainly widows and bereaved mothers, began laying flowers on graves of Confederate dead before the war ended. Many people today think that this tradition continued as a separate Southern practice called Decoration Day, while it was the North that practiced Memorial Day.
While not exactly wrong, it's not altogether true. Beginning with a proclamation by Gen. John Logan, national commander of the Grand Army of the Republic, Memorial Day was first widespread observed in 1868 to honor the dead of the Civil War. Graves of both Union and Confederate dead at Arlington Cemetery were decorated with flowers.
By 1890, all the states of the former northern Union recognized the day, but it still honored only Civil War dead. Southern states did not join in observing this day, continuing to honor Confederate dead on other dates (not uniform across the South). People generally think that this day was called Decoration Day, but I cannot find any citation to confirm it. (The old CSA memorializing of Confederate dead is still on the books of many Old South states; it is June 3 here in Tennessee.)
After World War I, the dead of that war were added to the honor roll of Memorial Day, then almost immediately the dead of all American wars. At that, the Southern states joined in and there has been a unified observance since.
Memorial Day was generally an observance by the several states until President Lyndon B. Johnson issued a proclamation in 1966 designating May 30 as national Memorial Day. There the day remained until Congress passed legislation in 1971 called the National Holiday Act. The Act made Memorial Day and most other federal holidays always occur on a Monday. Whether this served to strip the day of its solemn meaning I'll leave it to you to evaluate.
Unlike Veterans Day, Nov. 11, Memorial Day is a unique American holiday. The other English-speaking nations observe Nov. 11, the date World War I ended, just as we do. However, the observance is called Remembrance Day in Canada, Australia, Bermuda and some other lands of the former British Empire. New Zealand observes Nov. 11 in a low key way, the main observance being ANZAC Day, April 25. In the United Kingdom Nov. 11 is also commemorated in a low-key manner, the main observance being the second Sunday of November, called Remembrance Sunday.
In these nations, commemorations accomplish in one day what Memorial Day and Veterans Day do in America.