Boys Union Officer CostumeHalloween can be both fun and educational when your child wears the Boy's Union Officer Costume. Available to order in large or medium child's sizes, the historical set includes blue pants and a shirt. During the Civil War, the Union had a big advantage over the Confederacy. Most of the nation's industry was in the North and the North had a larger population. The Union army was twice as large as the Confederate army and much better supplied.