The 91st Pennsylvania Volunteer Infantry was a Union infantry regiment which fought in multiple key engagements of the American Civil War, including the Battle of Fredericksburg, Battle of Chancellorsville and Battle of Gettysburg. It was established through the combined efforts of Edgar M. Gregory, who had received approval from the U.S. War Department to begin recruiting soldiers for an entirely new regiment during the fall of 1861, and Edward E. Wallace, who had initiated his own recruitment efforts that October. Their recruits were volunteers, the majority of whom initially enlisted for three-year terms of service from their hometown of Philadelphia; they were divided into 10 lettered companies upon muster in during early December 1861: A, B, C, D, E, F, G, H, I, and K. (In later years