Colonel James Mulligan led the Irish Brigade in the Civil War. Senator Stephen M. Douglas and Mayor John Wentworth were popular among Chicago's Irish Democrats, and when they backed the North, the Irish responded to the call to arms. When Mulligan and his regiment was captured in Missouri, he escaped and formed a new all-volunteer brigade. Colonel Mulligan was killed on July 26, 1864, fighting in the Shenandoah Valley.
Calvary Cemetery was newly established at the time of Mulligan's death, and he was given a place of honor immediately inside the main (west) gate. Mulligan's monument is always planted with flowers.