When the 9th Pennsylvania Reserves mustered into Federal service on the 28th of May 1861, the enlistments for its men were for a period of three years or the duration of the war. Of the men who were mustered in at the Regiment's beginning (and survived its horrors), they would see the end of their military obligation at the Regiment's mustering-out on the 13th of May 1864. However, due to the 9th Reserves' exhaustive combat role for those three years, the many vacancies in the ranks would be filled with new recruits. These surviving men (seventy-two according to the roll), who had not fulfilled their three years of Federal service by the spring of '64, were not mustered out but instead were quickly transferred into a new Federal regiment, the One Hundred and Ninetieth Pennsylvania Volunteer Infantry (190th P.V.I.)
The 190th P.V.I. was mustered into Federal service on the 30th of May 1864. Ninety-one men of the 9th Reserves (nineteen veterans had re-enlisted to "finish the thing") were to form Company "K" of the 190th. The men recruited from the 9th Reserves were as follows:
The 190th P.V.I. saw its first action at Cold Harbor, along with the newly-formed 191st P.V.I. (the 191st being formed with veterans from the 10th Penna. Reserves). After Cold Harbor these two regiments became the Third Brigade, Third Division, of the Fifth Corps. The new Brigade began its service with a hard start when it was attacked at Charles City Cross Roads on the 13th of June, where it held at bay a superior number of the rebel forces. In the Petersburg Campaign the 190th would see its share of the fighting. Arriving in the evening on the 17th of June, their brigade was ordered to take an enemy position, and in their performance, they were to capture the entire 39th North Carolina Regiment. The brigade held this position until relieved despite the heavy losses due to continuous artillery and infantry assaults. These heavy losses would continue for the next eight days of constant active duty. Their brigade would see some relief from battle during the first two weeks of July; but instead of a rest, they would be engaged in the construction of Fort Warren. With that task completed, the brigade would take up positions in the vicinity of Fort Crawford until August.
On the 18th of August the 190th and 191st would capture and destroy a portion of the Weldon Railroad outside Petersburg; however on the next day, the entire brigade would be surrounded and captured. Those captured would suffer the remainder of the war as prisoners, but this would not be the end of the 190th. Fortunately a small detachment that had been sent to secure food and ammunition on the 19th of August was spared capture. These men would be the nucleus of the reformed 190th P.V.I. The reformed 190th, with its new recruits and old veterans, would see the end of the war leading the advance at Five Forks on the 1st of April and finishing their last combative role as skirmishers from the 2nd until the 9th of April. After Lee's surrender, the 190th returned to Washington where it went into camp until it was mustered out of service on the 28th of June 1865. Here was the end of a long service for those few survivors who had enlisted in 1861.