According to "Memorial Day: A Commemoriation," Memorial Day, initially referred to as Decoration Day, was observed by many communities after the Civil War, when the nation suffered more than 620,000 military deaths, roughly 2 percent of the total population at the time. John A. Logan, the Commander-in-Chief of the Grand Army of Republic, chose May 30, 1868, as a day to decorate the graves of Union troops across the nation.

From this beginning, Memorial Day is now designated as an annual day of remembrance to honor all those who have died in service to the United States during peace and war. 

Veterans Day, November 11, celebrates the service of all U.S. military veterans.

The red poppy has been a symbol of lives lost to war since World War I (1914–1918). Sales of red poppies benefit veterans associations and fund many charities and veterans causes. 

The poppy symbolism started with a poem written by   Canadian artillery unit brigade surgeon Lieutenant Colonel John McCraewho  saw bright-red poppies blooming on the war-torn fields where so many soldiers had lost their lives.

The red poppies reminded McCraewho of the blood spilled by the solider who died there. He wrote :

In Flanders fields the poppies blow

Between the crosses, row on row,
That mark our place; and in the sky
The larks, still bravely singing, fly
Scarce heard amid the guns below.

We are the Dead. Short days ago
We lived, felt dawn, saw sunset glow,
Loved and were loved, and now we lie,

In Flanders fields.

Take up our quarrel with the foe:
To you from failing hands we throw
The torch; be yours to hold it high.
If ye break faith with us who die
We shall not sleep, though poppies grow
In Flanders fields.