When the Civil War broke out, Getty was stationed at Fort Randall, Dakota Territory. On 14 May 1861 he was transferred to the Fifth Artillery and for a time was stationed at Fort Monroe, on the end of the Virginia Peninsula. On 28 September he was commissioned lieutenant colonel of volunteers. That fall he served as chief of artillery to General Joseph Hooker's division, deployed along the Lower Potomac. In the Peninsula campaign the following spring, he commanded a four-battery brigade of the artillery reserve in the siege of Yorktown and the battles of Gaines' Mill and Malvern Hill. When Confederate general Robert E. Lee invaded Maryland that fall, Getty was involved in the resulting battles of South Mountain and Antietam, where he served as chief of artillery for General Ambrose Burnside's IX Corps. Union artillery performed well at Antietam, prompting their opposite numbers in the Confederate army, their chief targets, to dub the battle "artillery hell." Getty was recognized for his part in this success with promotion to brigadier general of volunteers on 25 September 1862, just eight days after the battle. The next month he took command of one of the infantry divisions of the IX Corps, which he led at the battle of Fredericksburg, 13 December 1862.
Steven E. Woodworth, "Getty, George Washington," American National Biography Online, February 2000, http://www.anb.org/articles/05/05-00273.html.