When Jasper was in the Civil War, what side was he fighting on?

Well, he was born in Houston, TX and was in Galveston, TX when he was changed, so I would assume the South. That's just going on what he tells in his story.

I'm pretty sure he was fighting for the south.

Jasper states in Eclipse that he joined the Confederate Army, that means he was fighting for the South

Eclipse page 292