Each nation inside the Union had its very own specific regimental flags at some point of the Civil War

https://jaidenbnki358.clearhavendigest.com/posts/reenacting-the-past-the-significance-of-using-authentic-civil-war-flags-3

Each nation inside the Union had its personal original regimental flags all through the Civil War, reflecting regional satisfaction and exotic histories tied to their participation in the clash.