The practice of decorating soldiers' graves with flowers is an ancient custom. Soldiers' graves were decorated in the U.S. before and during the U.S. Civil War. There is documentation that women in Savannah, Georgia decorated soldiers' graves in 1862. In 1863, the cemetery dedication at Gettysburg, PA was a ceremony of commemoration at the graves of dead soldiers. Local historians in Boalsburg, PA, claim that ladies there decorated soldiers' graves on July 4, 1864. As a result, Boalsburg promotes itself as the birthplace of Memorial Day.
Following President Abraham Lincoln's assassination in April 1865, there were a variety of events of commemoration. The first known observance of a Memorial Day-type observance was in Charleston, South Carolina on May 1, 1865. During the war, Union soldiers who were prisoners of war had been held at the Charleston Race Course; at least 257 Union prisoners died there and were hastily buried in unmarked graves. Together with teachers and missionaries, Blacks in Charleston organized a May Day ceremony in 1865, which was covered by the New York Tribune and other national papers. The freedmen had cleaned up and landscaped the burial ground, building an enclosure and an arch labeled, "Martyrs of the Race Course." Nearly ten thousand people, mostly freedmen, gathered on May 1 to commemorate the dead. Involved were 3,000 schoolchildren newly enrolled in freedmen's schools, mutual aid societies, Union troops, and black ministers and white northern missionaries. Most brought flowers to lay on the burial field. Today the site is used as Hampton Park.. Years later, the celebration would come to be called the "First Decoration Day" in the North.
David W. Blight described the day:
"This was the first Memorial Day. African Americans invented Memorial Day in Charleston, South Carolina. What you have there is black Americans recently freed from slavery announcing to the world with their flowers, their feet, and their songs what the War had been about. What they basically were creating was the Independence Day of a Second American Revolution.”Professor Blight admitted, however, that this event in Charleston did not lead to the establishment of Memorial Day across the country.
The sheer number of dead soldiers, both Union and Confederate, who perished in the civil war meant that burial and memorialization would take on new cultural significance. Particularly under the leadership of women during the war, an increasingly formal practice of decorating graves had already taken shape. In 1865, the federal government began a program of creating national military cemeteries for the Union dead.
In the NorthThe friendship between General John Murray, a distinguished citizen of Waterloo, New York, and General John A. Logan, who helped bring attention to the event nationwide, was likely a factor in the holiday's growth. On May 5, 1868, in his capacity as commander-in-chief of the Grand Army of the Republic - the organization for Union Civil War veterans - Logan issued a proclamation that "Decoration Day" should be observed nationwide. It was observed for the first time on May 30 of the same year; the date was chosen because it was not the anniversary of a battle.
Events were held in 183 cemeteries in 27 states in 1868, and 336 in 1869. The northern states quickly adopted the holiday; Michigan made "Decoration Day" an official state holiday in 1871 and by 1890, every northern state followed suit. The ceremonies were sponsored by the Women's Relief Corps, which had 100,000 members. By 1870, the remains of nearly 300,000 Union dead had been reinterred in 73 national cemeteries, located near the battlefields and therefore mostly in the South. The most famous are Gettysburg National Cemetery in Pennsylvania and Arlington National Cemetery, near Washington.
The Memorial Day speech became an occasion for veterans, politicians and ministers to commemorate the War - and at first to rehash the atrocities of the enemy. They mixed religion and celebratory nationalism and provided a means for the people to make sense of their history in terms of sacrifice for a better nation. People of all religious beliefs joined together, and the point was often made that the German and Irish soldiers had become true Americans in the "baptism of blood" on the battlefield. By the end of the 1870s much of the rancor was gone, and the speeches praised the brave soldiers both Blue and Gray. By the 1950s, the theme was American exceptionalism and duty to uphold freedom in the world.
Ironton, Ohio, lays claim to the nation's oldest continuously running Memorial Day parade. Its first parade was held May 5, 1868, and the town has held it every year since. However, the Memorial Day parade in Doylestown, Pennsylvania, predates Ironton's by one year. 
Memorial Day for me is also deeply personal, since my late husband's side of the family fought in the Civil War (Union side-Army) and the Spanish-American War--My Grandfather served in the Army during WWI; One Uncle served in the Navy during WWII and other Uncle and Aunt both served in the Navy at the start of the Cold War; my late father served in the Air Force during the Korean War; my brother-in-law served in the Army during Vietnam and I was in the Army Reserve at the end of the Cold War(1980-1992).