The organization of the volunteer Confederate forces under Brig. Gen. Beauregard into the I Corps, Army of the Potomac, was announced on June 20, 1861. There were then 6 brigades, which number was increased later to 8. The strength of the corps was about 30,000 men.
A division organization was afterward adopted, and 1 of these divisions, commanded by Maj. Gen. James Longstreet, was denominated the Center of Position, Army of Northern Virginia, at the opening of the Peninsula campaign. It contained about 14,000 men. As the 2nd Division (or Corps) of the army, the troops fought from Fair Oaks, where they were known as the Right Wing, through the Seven Days' battles.
Toward the end of July, the army was further concentrated into commands of which one, consisting of 6 divisions, was headed by Longstreet, and this, during the campaign against Maj. Gen. John Pope, was called the Right Wing or Longstreet's Corps. After the battle of Antietam, the corps was designated the I Corps, Army of Northern Virginia.
In September, 1863, Gen. Robert E. Lee sent the corps, with the exception of Brig. Gen. Pickett's division, to assist Maj. Gen. Braxton Bragg, and, as Longstreet's Corps, fought in the Army of Tennessee at Chickamauga and remained in East Tennessee until April, 1864, when it rejoined the Army of Virginia.
Maj. Gen. R. H. Anderson succeeded to the command of the corps after Longstreet was wounded at the battle of the Wilderness, May 6th. The latter returned to his corps, October 19th, and continued at the head until the surrender at Appomattox.
