The Union Guards were heavily engaged on both December 11 and December 13, 1862, at the Battle of Fredericksburg. During the Chancellorsville Campaign in early May 1863, the 59th supported Sedgwick's actions against Marye's Heights. In June, the command of the regiment changed dramatically after Colonel William Northedge resigned due to charges of corruption and drunkenness on duty. Lieutenant Colonel Max A. Thoman replaced Northedge as commander. Under Thoman's leadership, the small number of the 59th marched with the rest of Colonel Norman J. Hall's brigade of Brig. Gen. John Gibbon's division into Pennsylvania during the Gettysburg Campaign.