The "Battle Hymn of the Republic" was a Union fight song. Nobody celebrating their Southern heritage would sing this song.
Missouri was a slave state that never joined the Confederacy. Much, if not most, of the population wanted to secede but the state was isolated and would be unsupported by the Confederacy. The governor and other state leaders wisely kept Missouri in the Union (the Republic) and saved the state from much of devastation experienced by other southern states. Many Confederate sympathizers joined private militias. A well-known example is Quantrill's Raiders. These guerrilla fighters. Other sympathizers joined the Confederate Army, but they had to travel to a Confederate state to do so.
Missouri was a slave state that never joined the Confederacy. Much, if not most, of the population wanted to secede but the state was isolated and would be unsupported by the Confederacy. The governor and other state leaders wisely kept Missouri in the Union (the Republic) and saved the state from much of devastation experienced by other southern states. Many Confederate sympathizers joined private militias. A well-known example is Quantrill's Raiders. These guerrilla fighters. Other sympathizers joined the Confederate Army, but they had to travel to a Confederate state to do so.