Memorial Day is an American holiday, observed on the last Monday of May, honoring the men and women who died while serving in the U.S. military.
Originally known as Decoration Day, it originated in the years following the Civil War and became an official federal holiday in 1971. Many Americans observe Memorial Day by visiting cemeteries or memorials, holding family gatherings and participating in parades. Unofficially, it marks the beginning of the summer season.
The Civil War, which ended in the spring of 1865, claimed more lives than any conflict in U.S. history and required the establishment of the country’s first national cemeteries.
By the late 1860s, Americans in various towns and cities had begun holding springtime tributes to these countless fallen soldiers, decorating their graves with flowers and reciting prayers.
It is unclear where exactly this tradition originated; numerous different communities may have independently initiated the memorial gatherings. And some records show that one of the earliest Memorial Day commemorations was organized by a group of formerly enslaved people in Charleston, South Carolina less than a month after the Confederacy surrendered in 1865. Nevertheless, in 1966 the federal government declared Waterloo, New York, the official birthplace of Memorial Day.
From history.com -> https://www.history.com/topics/holidays/memorial-day-history