Pennsylvania Reserves The Pennsylvania Reserves were an infantry division in the Union Army during the American Civil War . Noted for its famous commanders and high casualties , it served in the Eastern Theater , and fought in many important battles , including Antietam and Gettysburg . Organization . When President Abraham Lincoln called for volunteers to " put down the rebellion " in the spring of 1861 , the commonwealth of Pennsylvania found itself with more volunteers than needed to meet its Federal quota . The Secretary of War , Simon Cameron , was a political enemy of Andrew Curtin , Pennsylvania governor , and refused to take the extra men into Federal service . Curtin decided to retain the extra men and organized , trained , and equipped them at state expense . The creation of the special division was approved by the Pennsylvania legislature on May 15 , 1861 . The men were trained at camps of instruction in four cities : Easton , Pittsburgh , West Chester , and Harrisburg . The training camp near Harrisburg was named Camp Curtin for the governor . Fifteen regiments were formed , known as the 1st through 15th Pennsylvania Reserves ( they were later designated the 30th through 44th Pennsylvania Volunteers , but generally retained the label of the Pennsylvania Reserves ) . At the time of the redesignation , Pennsylvania had other troops both in the field or in various stages of development using the same numbers . While many of these units used their designations into middle and late 1862 , much confusion arose over the naming convention . Additional naming confusion occurred within the ranks of the reserves . The 13th Pennsylvania Reserve Regiment ( 42nd Pennsylvania Volunteers ) was additionally named the 1st Pennsylvania Rifles . Although better known as the " Bucktails , " this regiment became officially known as the First Rifles . The same can be said regarding the 14th and 15th Pennsylvania Reserves ( 43rd and 44th Pennsylvania Volunteers ) , which officially were designated as the 1st Pennsylvania Light Artillery and the 1st Pennsylvania Cavalry , respectively . The regiments were grouped into a division of three brigade s , and the entire unit normally fought together until the initial enlistments expired in 1864 . The exceptions to this include the 2nd Brigade , most of which did not take part at Gettysburg , as it was assigned to the Washington , D . C . , defenses , and the detachment of several artillery batteries and cavalry troops to other divisions . Command history . The first commander was George A . McCall , and later division commanders were John F . Reynolds , George G . Meade , and Samuel W . Crawford . Truman Seymour twice was acting commander , once on the Peninsula and once at Antietam , when Meade became acting commander of I Corps . The initial brigade commanders were Reynolds , Meade , and Colonel John S . McCalmont ( until Edward Otho Cresap Ord took official command of the 3rd Brigade ) . History . Initially assigned to I Corps , in June 1862 , the division was transferred to the Virginia Peninsula where it served with the V Corps of the Army of the Potomac during the Peninsula Campaign . The division then returned to its old corps ( which was at the time designated III Corps in the Army of Virginia ) during the Second Bull Run Campaign . The division ' s parent formation resumed its I Corps designation just prior to the Antietam campaign when it rejoined the Army of the Potomac . The division participated in the battles of South Mountain , Antietam , and Fredericksburg , particularly distinguishing itself at Fredericksburg , where it penetrated the Confederate lines . Between Fredericksburg and Gettysburg , the division was a part of the XXII Corps assigned to Washington , D . C . It was part of the V Corps again for the Battle of Gettysburg , where it distinguished itself on July 2 , 1863 , fighting around Little Round Top . One brigade drove Confederate forces from the western slopes of Little Round Top back to the Wheatfield . Under Crawford , the Pennsylvania Reserves continued to fight with the Army of the Potomac until just before the Battle of the Bethesda Church or Battle of Totopotomoy Creek , when the men ' s three - year enlistments expired . A large number of the men re - enlisted and became the 190th and 191st Pennsylvania Volunteers and fought until the end of the war .