Ah, Shanti - I wish I would have remembered that it was on Connie Dover's The Border of Heaven. Here's what she says in the album notes:

Approximately 160,000 Irish-born troops fought for the Union during the American Civil War, some fighting in all-Irish units such as the Irish Brigade, which grew to five regiments from New York City, Boston, and Philadelphia. However, Ireland officially sided with the South, and many Irish fought with the Southern units. In an attack at Vicksburg, Mississippi in 1863, five men of the 7th Missouri Infantry were shot down while trying to keep their green flag aloft in a ditch beneath the enemy's ramparts. In the 1862 Battle of Fredericksburg (Virginia) the Irishmen of the 24th Georgia Infantry cheered the bravery of the charging Irish Brigade before mowing down their countrymen (Kansas City Star, March 17, 1998).
One of my sources for this song is from the singing of Mrs. Emma Dusenberry of Mena, Arkansas, as printed in Ozark Folksongs, edited by Vance Randolph. Versions also exist in Tennessee, Illinois, and Missouri. The latter state was the scene of some of the war's bloodiest fighting, particularly along its western border with Kansas, where continued violence between "Free Staters" and "Border Ruffians" terrorized inhabitants and kept the region in a state of turbulence for over a decade. The melody is derived from "Barbry Ellen," an American variant of the well-known Scottish ballad, "Barbara Allen."

-Joe Offer-