The 91st PA's battles
Because of poor generalship, the 91st had no spectacular successes on the battlefield. They arrived the day after Antietam was over. Hooker kept the entire Fifth Corps in reserve during Chancellorsville, instead of using them at the crucial point. They would have been part of the force defending Little Round Top at Gettysburg, except that General Sickles compounded his error by sending them to defend an exposed battery. They took--twice!--a crucial hill during Spotsylvania, which the Union needed for Grant to attack the Confederates, but he never attacked. And they captured the place by Petersburg where the mine was exploded, an opportunity wasted by a last-minute change forced by General Grant, together with General Burnside's response to it.
Weapons The 91st's weapon was the Springfield Rifled Musket.
Numbers Although the regiment was supposed to have 810 to 990 men, it often had less than one-half that number present. Once it had only 75 men present for duty. This happened partly because of deaths, injuries, and illnesses, and partly because men were assigned to duty elsewhere.
Zouave training For at least a short while, the 91st drilled the zouave drills; whether they ever wore the uniform is unclear.