I Corps (First Corps) was the designation of three different

corps Corps (; plural ''corps'' ; from French , from the Latin "body") is a term used for several different kinds of organization. A military innovation by Napoleon I, the formation was first named as such in 1805. The size of a corps varies great ...

-sized units 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 ...

during 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 ...

. Separate formation called the I Corps served in the

Army of the Ohio The Army of the Ohio was the name of two Union armies in the American Civil War. The first army became the Army of the Cumberland and the second army was created in 1863. History 1st Army of the Ohio General Orders No. 97 appointed Maj. Gen. Do ...

Army of the Cumberland The Army of the Cumberland was one of the principal Union armies in the Western Theater during the American Civil War. It was originally known as the Army of the Ohio. History The origin of the Army of the Cumberland dates back to the creation ...

under Alexander M. McCook from September 29, 1862 to November 5, 1862, in the

Army of the Mississippi Army of the Mississippi was the name given to two Union armies that operated around the Mississippi River, both with short existences, during the American Civil War. History 1862 The first army was created on February 23, 1862, with Maj. Gen ...

under

George W. Morgan George Washington Morgan (September 20, 1820 – July 26, 1893) was an American soldier, lawyer, politician, and diplomat. He fought in the Texas Revolution and the Mexican–American War, and was a general in the Union Army during the Ameri ...

from January 4, 1863 to January 12, 1863 (which was the re-designated

XIII Corps (ACW) XIII Corps was a corps of the Union Army during the American Civil War. It was first led by Ulysses S. Grant and later by John A. McClernand and Edward O.C. Ord. It served in the Western Theater of civil war, Trans-Mississippi Theater and a ...

), and in the

Army 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 ...

and

Army of Virginia The Army of Virginia was organized as a major unit of the Union Army and operated briefly and unsuccessfully in 1862 in the American Civil War. It should not be confused with its principal opponent, the Confederate Army of ''Northern'' Virginia ...

(see below). The first two were units of very limited life; the third was one of the most distinguished and veteran corps in the entire Union Army, commanded by very distinguished officers. The term "First Corps" is also used to describe the

First Veteran Corps The Veteran Reserve Corps (originally the Invalid Corps) was a military reserve organization created within the Union Army during the American Civil War to allow partially disabled or otherwise infirm soldiers (or former soldiers) to perform lig ...

from 1864 to 1866.

History

The I Corps was created on March 3, 1862, when

President President most commonly refers to: *President (corporate title) *President (education), a leader of a college or university *President (government title) President may also refer to: Automobiles * Nissan President, a 1966–2010 Japanese ful ...

Abraham Lincoln Abraham Lincoln ( ; February 12, 1809 – April 15, 1865) was an American lawyer, politician, and statesman who served as the 16th president of the United States from 1861 until his assassination in 1865. Lincoln led the nation thro ...

ordered the creation of a five-corps

army An army (from Old French ''armee'', itself derived from the Latin verb ''armāre'', meaning "to arm", and related to the Latin noun ''arma'', meaning "arms" or "weapons"), ground force or land force is a fighting force that fights primarily on ...

, then under the command of

Major General Major general (abbreviated MG, maj. gen. and similar) is a military rank used in many countries. It is derived from the older rank of sergeant major general. The disappearance of the "sergeant" in the title explains the apparent confusion of a ...

George B. McClellan George Brinton McClellan (December 3, 1826 – October 29, 1885) was an American soldier, Civil War Union general, civil engineer, railroad executive, and politician who served as the 24th governor of New Jersey. A graduate of West Point, McCl ...

. The first commander of the corps was Major General

Irvin McDowell Irvin McDowell (October 15, 1818 – May 4, 1885) was a career American army officer. He is best known for his defeat in the First Battle of Bull Run, the first large-scale battle of the American Civil War. In 1862, he was given command o ...

. It contained three divisions under the commands of Brigadier Generals William B. Franklin, George A. McCall, and

Rufus King Rufus King (March 24, 1755April 29, 1827) was an American Founding Father, lawyer, politician, and diplomat. He was a delegate for Massachusetts to the Continental Congress and the Philadelphia Convention and was one of the signers of the Unit ...

McClellan originally intended for the I Corps to participate in his Peninsula Campaign with the rest of the army, but after

Stonewall Jackson Thomas Jonathan "Stonewall" Jackson (January 21, 1824 – May 10, 1863) was a Confederate general during the American Civil War, considered one of the best-known Confederate commanders, after Robert E. Lee. He played a prominent role in nearl ...

initiated his Valley Campaign on March 23 at the

First Battle of Kernstown The First Battle of Kernstown was fought on March 23, 1862, in Frederick County and Winchester, Virginia, the opening battle of Confederate Maj. Gen. Thomas J. "Stonewall" Jackson's campaign through the Shenandoah Valley during the American ...

, President Lincoln decided to keep the corps in northern Virginia to protect Washington. On April 4, Lincoln created the ''Department of the Rappahannock'', detaching the I Corps from the

to form the core of the new department, and giving command of the department to I Corps commander, Irvin McDowell. In May, Franklin’s division was detached and sent south to reinforce McClellan in his Peninsula campaign, uniting with a division of the IV Corps to form the

VI Corps 6 Corps, 6th Corps, Sixth Corps, or VI Corps may refer to: France * VI Cavalry Corps (Grande Armée), a cavalry formation of the Imperial French army during the Napoleonic Wars * VI Corps (Grande Armée), a formation of the Imperial French army du ...

. On June 18, McCall’s division, the “

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 ...

”, was also detached and sent to join McClellan’s army on the

Virginia Peninsula The Virginia Peninsula is a peninsula in southeast Virginia, USA, bounded by the York River, James River, Hampton Roads and Chesapeake Bay. It is sometimes known as the ''Lower Peninsula'' to distinguish it from two other peninsulas to the ...

. Temporarily attached to the

V Corps 5th Corps, Fifth Corps, or V Corps may refer to: France * 5th Army Corps (France) * V Cavalry Corps (Grande Armée), a cavalry unit of the Imperial French Army during the Napoleonic Wars * V Corps (Grande Armée), a unit of the Imperial French Ar ...

, it saw heavy action at Gaines' Mill and

Glendale Glendale is the anglicised version of the Gaelic Gleann Dail, which means ''valley of fertile, low-lying arable land''. It may refer to: Places Australia * Glendale, New South Wales ** Stockland Glendale, a shopping centre *Glendale, Queensland, ...

. Division commander Brig. Gen.

George McCall George Archibald McCall (March 16, 1802 – February 25, 1868) was a United States Army officer who became a brigadier general and prisoner of war during the American Civil War. He was also a naturalist. Biography McCall was born in Philadel ...

and future I Corps commander Brig. Gen. John Reynolds were both captured and freed in a prisoner exchange that August. On June 26, Rufus King’s division,

James B. Ricketts James Brewerton Ricketts (June 21, 1817 – September 22, 1887) was a career officer in the United States Army, serving as a Union Army general during the Civil War. At First Bull Run, he was wounded and captured, but later exchanged. He fought a ...

’ division, and Abner Doubleday’s brigade were transferred from the Department of the Rappahannock to the newly created

, forming its III Corps, under the command of Irvin McDowell. On August 26, the “Pennsylvania Reserves” were transferred to the III Corps of the Army of Virginia and fought at the

Second Battle of Bull Run The Second Battle of Bull Run or Battle of Second Manassas was fought August 28–30, 1862, in Prince William County, Virginia, as part of the American Civil War. It was the culmination of the Northern Virginia Campaign waged by Confederate ...

. Soon after the battle, the corps was transferred to the Army of the Potomac and reclassified as the I Corps of the Army of the Potomac.

In early September, the I Corps, now under the command of Major General

Joseph Hooker Joseph Hooker (November 13, 1814 – October 31, 1879) was an American Civil War general for the Union, chiefly remembered for his decisive defeat by Confederate General Robert E. Lee at the Battle of Chancellorsville in 1863. Hooker had serv ...

, followed Lee through Maryland and fought at South Mountain and

Antietam The Battle of Antietam (), or Battle of Sharpsburg particularly in the Southern United States, was a battle of the American Civil War fought on September 17, 1862, between Confederate Gen. Robert E. Lee's Army of Northern Virginia and Union G ...

. John Reynolds (who had been elevated to division command of the Reserves) was temporarily detached to train militia troops in his home state of Pennsylvania and did not participate in the Maryland Campaign. At Antietam, the I Corps was the first corps engaged, and suffered enormous losses in the fighting around the cornfield and Dunker Church. Hooker was wounded in the foot during the battle and command of the I Corps devolved on Meade (the ranking division commander). In October, Reynolds returned and was made commander of the corps. Having fought three battles in six weeks, the I Corps was severely depleted. An influx of new volunteer regiments (both three year and nine month) arrived to replenish its ranks, and by November it was back up to full strength. The corps moved southward to fight General Robert E. Lee's army at the

Battle of Fredericksburg The Battle of Fredericksburg was fought December 11–15, 1862, in and around Fredericksburg, Virginia, in the Eastern Theater of the American Civil War. The combat, between the Union Army of the Potomac commanded by Maj. Gen. Ambrose Burnsi ...

, commanded by Major General John F. Reynolds, arguably the best Union corps commander in the Eastern Theater. At Fredericksburg, Meade and John Gibbon's divisions fought Stonewall Jackson's corps south of the town while Doubleday's division was held in reserve. The I Corps did not see any significant action in the Chancellorsville Campaign. John Reynolds death

In its last major battle, the

Battle of Gettysburg The Battle of Gettysburg () was fought July 1–3, 1863, in and around the town of Gettysburg, Pennsylvania, by Union and Confederate forces during the American Civil War. In the battle, Union Major General George Meade's Army of the Po ...

, General Reynolds was killed just as the first troops arrived on the field, and command was inherited by Major General

Abner Doubleday Abner Doubleday (June 26, 1819 – January 26, 1893) was a career United States Army officer and Union major general in the American Civil War. He fired the first shot in defense of Fort Sumter, the opening battle of the war, and had a pi ...

. Although putting up a ferocious fight, the I Corps was overwhelmed by the

Confederate Confederacy or confederate may refer to: States or communities * Confederate state or confederation, a union of sovereign groups or communities * Confederate States of America, a confederation of secessionist American states that existed between 1 ...

Third Corps (

A.P. Hill Ambrose Powell Hill Jr. (November 9, 1825April 2, 1865) was a Confederate general who was killed in the American Civil War. He is usually referred to as A. P. Hill to differentiate him from another, unrelated Confederate general, Daniel Harvey H ...

) and

Robert E. Rodes Robert Emmett (or Emmet) Rodes (March 29, 1829 – September 19, 1864) was a Confederate general in the American Civil War, and the first of Robert E. Lee's divisional commanders not trained at West Point. His division led Stonewall Jackso ...

's division of

Richard S. Ewell Richard Stoddert Ewell (February 8, 1817 – January 25, 1872) was a career United States Army officer and a Confederate general during the American Civil War. He achieved fame as a senior commander under Stonewall Jackson and Robert E. L ...

's Second Corps. It was forced to retreat through the town of Gettysburg, taking up defensive positions on Cemetery Hill after the 16th Maine's brave stand of which only 39 soldiers returned. The next day (July 2, 1863), the command was given to Major General

John Newton John Newton (; – 21 December 1807) was an English evangelical Anglican cleric and slavery abolitionist. He had previously been a captain of slave ships and an investor in the slave trade. He served as a sailor in the Royal Navy (after forc ...

, a division commander from the

. This was a controversial move that deeply offended the more senior Doubleday. Newton led it through the remainder of the battle, including the defense against

Pickett's Charge Pickett's Charge (July 3, 1863), also known as the Pickett–Pettigrew–Trimble Charge, was an infantry assault ordered by Confederate General Robert E. Lee against Major General George G. Meade's Union positions on the last day of the B ...

, and through the

Mine Run Campaign The Battle of Mine Run, also known as Payne's Farm, or New Hope Church, or the Mine Run campaign (November 27 – December 2, 1863), was conducted in Orange County, Virginia, in the American Civil War. An unsuccessful attempt of the Union ...

that fall. On March 24, 1864, the Civil War career of the I Corps came to an end as it was disbanded and its depleted units were reorganized into two divisions, which were transferred into the

of the Army of the Potomac.

Command history

* As III Corps,

References

*Eicher, John H., & Eicher, David J.: ''Civil War High Commands'', Stanford University Press, 2001, *Fox, William F.: ''Regimental Losses in the American Civil War'', Albany Publishing, 1889
online text of I Corps section
*Wipperman, Darin: ''First for the Union: Life and Death in a Civil War Army Corps from Antietam to Gettysburg'', Stackpole, 2020 {{Gettysburg Campaign 01 Military units and formations established in 1862 1862 establishments in the United States Military units and formations disestablished in 1864