If anyone is still interested - I'm doing research on Mulligan's Brigade, 23rd regiment Illinois Volunteers. Here's what I have: John Rourke or O'Rourke enlisted in 6th Wisconsin Infty and resigned in Nov 1861. He was born in County Limerick Ireland. He raised a battery in Wisconsin, the 11th Wisconsin Arty. The Battery was recruited by Col Mulligan in Dec 1861. They moved to Chicago from Madison Wisconsin in Jan 1862 . The battery was accepted by the Governor of Illinois as Batty L, 1st Light Light Arty. It was also called "Mulligan's Brass Band." An Ordnance Report for Sep 1863 showed Batty L: 2 12-pounder Model 1857 and 4 James Rifles.

Capt John Rourke was quite a fellow. He raised a Wisconsin Battery in Milwaukee, but enlisted and mustered it in Illinois. Come time for them to veteranize, quite an argument between Illinois and Wisconsin insued. In Jun 1862 the regiment, including Rourke's Battery moved by train to Harper's Ferry and then to New Creek, [W]Va. There were several example of Rourke being drunk on and off duty despite that fact, his Battery was quite proficient. In Nov 1862 the Officers of the 23rd Illinois "Irish Brigade" signed a petition formally dissociating themselves from Rourke because of his drunkenness and "ungentlemanly conduct." He was mentioned prominently in a Courts-Martial of one of his men as being the real problem, rather then the accused. In fact, Col Mulligan put him on a short leash, ordering him to report directly to Col Mulligan. Rourke, was captured in Jan 1863 and confined at Libby Prison in Richmond. He had a broken collar bone from falling from his horse. He was transferred to various prisons including Macon Charleston, and Columbia. He escaped from Columbia in Mar 1865, and made it to the Federal lines in Charleston. He died on May 5, 1882 at the Southern Hotel at St Louis, Mo., age 45 years, occupation, Banker., Cause of Death Congestion of Lungs.