I believe I heard it from Sam Hinton. I remember most of the verses, but not all. I looked over headings for over 100 Civil War songs (I neglected to specify @America) in the DT to no avail. Here's a few verses:

I'm just a damn Yankee Way down in the South
And I love to kiss Southern belles on the mouth.
I laugh when they say all damn Yankees are bad,
'Cause nobody knows I'm a damn Yankee lad.

CHORUS: And I'm having fun like I never have had
'Cause nobody knows I'm a damn Yankee lad.

When I found old Sherman had left me behind,
A very strange notion came into my mind.
I dressed up in gray and I made up my spiel,
And I headed straight for the town of Mobile.

I stopped in Atlanta and met a Creole.
She captured my heart and she captured my soul.
She fed me on cornbread and peaches and ham,
Not knowing that I was a damn Yankee man.

I've raised a fine family of girls and young men.
They think that damn Yankees are plum full of sin.
They'd call you a liar if you said that their dad
Had marched to Mobile as a damn Yankee lad.

When I get so old that I'm ready to die,
I'll put on my uniform blue as the sky.
They'll march round my coffin, and won't they be mad
When they learn that I was a damn Yankee lad?

I do declare, I damn near know it all - makes sense as is but I think there's a bit more? Can anyone supply missing or alternative verses?