Answer:
it for the people who served in the civil war.
The first time it was celebrated was May 1, 1865
also if your wandering how Did the civil war start.
The Civil War officially began when the Confederate States of America fired on the Fort Sumter, South Carolina in April 1861. The Confederacy was formed from slaveholding states that had seceded from the United States following the election of Abraham Lincoln in 1860.
if you need anymore information let me know if I can help.