"Earthworks only":

There's an old plantation house on the grounds of the Chalmette Battlefield, and I'm fairly sure that it dates back to the battle.

I attended the anniversary reenactment several years ago and heard the whole narrative as passed along by National Park Rangers, usually an authoritative source. My memory is not absolutely sure, but I think I recall discussion of the house as part of the environment during the battle, close behind the American line. Not a fortified military installation, but at least a building that could serve as a makeshift headquarters.

Bee-Dub: Thanks for the insight about the date and how it correlates to the fiddle-tune title. A lot of people might "know" those two facts but still fail to pur them together...