The Department of Pennsylvania (or General Patterson's Army) was a large military unit in the

Union Army During the American Civil War, the Union Army, also known as the Federal Army and the Northern Army, referring to the United States Army, was the land force that fought to preserve the Union (American Civil War), Union of the collective U.S. st ...

at the outset of the

American Civil War The American Civil War (April 12, 1861 – May 26, 1865; also known by other names) was a civil war in the United States. It was fought between the Union ("the North") and the Confederacy ("the South"), the latter formed by states th ...

. Established on April 27, 1861, its territory consisted of

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

Delaware Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent Del ...

, and all of

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

not embraced in the

Department of Annapolis Department may refer to: * Departmentalization, division of a larger organization into parts with specific responsibility Government and military *Department (administrative division), a geographical and administrative division within a country, ...

(later renamed Department of Maryland) and the

Department of Washington Department of Washington, was a department of the Union Army constituted on April 9, 1861. It consisted of the District of Columbia to its original boundaries, and the State of Maryland as far as Bladensburg. It was merged into the Military D ...

. Its remnants were absorbed into the short-lived Department of the Shenandoah on July 19, 1861, which also absorbed the Department of Maryland on July 25, and on August 24 was merged into the

Department of the Potomac The Army of the Potomac was the principal Union Army in the Eastern Theater of the American Civil War. It was created in July 1861 shortly after the First Battle of Bull Run and was disbanded in June 1865 following the surrender of the Confedera ...

History

It was under the command of Major General Robert Patterson, its manpower mainly consisted of three-month troops from the states of Pennsylvania and New York. After achieving a tactical victory at the

Battle of Hoke's Run The Battle of Hoke's Run, also known as the Battle of Falling Waters or Battle of Hainesville, took place on July 2, 1861, in Berkeley County, Virginia (now West Virginia) as part of the Manassas campaign of the American Civil War. Notable a ...

on July 2 and contributing indirectly to the Union disaster at the

First Battle of Bull Run The First Battle of Bull Run (the name used by Union forces), also known as the Battle of First Manassas

on July 21, its unexpired regiments and commanders were absorbed into the ''Department of the Shenandoah'' under the command of Major General Nathaniel P. Banks on July 25, 1861.

Pennsylvania Reserves

When President Abraham Lincoln called for 75,000 volunteers in the spring of 1861, the Commonwealth of Pennsylvania produced more than twice its quota. For political reasons the U.S. Secretary of War, Simon Cameron, rejected fifteen regiments for immediate service, and they became known as the 1st through 15th Pennsylvania Reserves. Pennsylvania elected to retain, organize, train and equip them at its own expense.
These fifteen regiments were unavailable either to Patterson in the Shenandoah Valley or to McDowell at

First Bull Run The First Battle of Bull Run (the name used by Union forces), also known as the Battle of First Manassas

. "Within four days after the disaster at Bull's Run, eleven regiments of this fine body of men (armed, drilled, clothed, equipped, and in all respects ready for active service) were in Washington," Governor Andrew G. Curtin reminded the State Legislature.

Battle of Hoke's Run

On July 2, 1861, Major General Robert Patterson's army, called the ''Department of Pennsylvania'', crossed the Potomac River near Williamsport, Maryland, and marched on the main road toward Martinsburg, Virginia. Near Hoke's Run, Union forces clashed with Confederate forces and slowly drove them back toward Winchester. Withdrawing before Patterson's larger force, Colonel Thomas J. Jackson accomplished his orders to delay the Federal advance. The encounter was very brief, and three regiments reported casualties: First Wisconsin Infantry, Eleventh Pennsylvania Infantry, and Fifteenth Pennsylvania Infantry. The Order of Battle shows all units in the organization at its peak size and structure.

First Battle of Bull Run

During the afternoon of July 21, 1861, the arrival of BG General Joseph E. Johnston reversed the tide of Battle, the ensuing Confederate counterattack turned victory into a rout, and euphoric Northern hopes for a short war were quickly dashed. Lieutenant General Winfield Scott had hoped that Patterson and his Department of Pennsylvania would prevent Johnston from reinforcing Beauregard at Manassas Junction, and when Johnston's troops became a major deciding factor, Patterson's actions became a subject of controversy. After the fact, Patterson believed: * He had requested from General Scott a direct order to attack Johnston and not received it; * He believed that the battle at Manassas would be fought on July 16, 1861, and his responsibility was to delay Johnston until the 16th; * He had successfully occupied Johnston through July 16 and for everaladditional days thereafter; * Without knowledge of the battle's nonoccurrence on July 16, he had promptly notified General Scott when Johnston actually left the Shenandoah Valley on July 20. * His entire course of action had been reviewed and approved by his subordinate officers, as ordered, and * He had fully complied with every direct order issued to him. Patterson was honorably discharged on July 27, 1861, and never received another commission. He sought to redress the record through every possible avenue, including a personal audience with President Abraham Lincoln, and later published his own version of events.

Recreation

On December 1, 1864, the Department of Pennsylvania was recreated, with the merging of the

Department of the Susquehanna The Department of the Susquehanna was a military department created by the United States War Department during the Gettysburg Campaign of the American Civil War. Its goal was to protect the state capital and the southern portions of the commonwealt ...

with the Department of the Monongahela. It operated until June 27, 1865, under the

Middle Military Division The Middle Military Division was an organization of the Union Army during the American Civil War, responsible for operations around the Shenandoah Valley of Virginia and the Valley Campaigns of 1864. In the summer of 1864, Confederate General Ju ...

References