Back when there was a big war called the Civil War, lots of soldiers fought for their sides. Some of these soldiers were part of a group called the Union. They were fighting to keep the United States of America together and free all people, no matter what color their skin was.
After the war, the sons of those Union soldiers decided to start a group called Sons of Union Veterans of the Civil War. They wanted to remember the brave soldiers who fought for the Union side and make sure people didn't forget how important the war was.
These sons of Union soldiers would get together and talk about what their dads told them about the war. They would also do things to honor those soldiers, like having parades or putting up monuments.
Today, people who are descendants of Union soldiers can still be part of this group and continue to remember and honor their ancestors.