We have copies of some documents relating to Edmund O'Dwyer.' These were obtained from the U. S. Army Military History Institute, Carlisle Barracks, Pa. For some reason I cannot access their unit bibliography for the 23rd this morning.
From their holdings, date unknown
O'Dwyer, Edmund - HCWRTColl (Pvt's incoming & outgoing letters, May 6, 1861-Mar 7, 1865; Dispatches sent to New York Tablet, Nov 12, 1862-Sep 27, 1864;
Obituary, May 6, 1865
I also have a copy of the sheet music celebrating the mortal wounding of Mulligan at the Battle of Kerstown "Lay Me Down and Save the Flag."
Of interest, four years ago traveling cross country, we visited the famous WWII North Platt, Nebraska Canteen. There we found prominently displayed the photo of Colonel Mulligan.
I would assume you have Mulligan's article "The Siege of Lexington, Mo.", Battles and Leaders of the Civil War, Vol. 1, pp. 307/13.