On March 13, 1862, Major General George B. McClellan issued General Order No. 101, reorganizing the Army of the Potomac into five corps, in compliance with president Abraham Lincoln's War Order No. 2.
Head-Quarters, Army of the Potomac,
Fairfax Court House, Va., March 13th, 1862
General Orders, No. 101:
In compliance with the President’s War Order, No. 2, of March 8th, 1862, the active portion of the Army of the Potomac, is formed into army corps, as follows:
1st Corps. Maj.-Gen. Irwin McDowell, to consist, for the present, of the divisions of Franklin, McCall, and King.
2nd Corps. Brig.-Gen. E.V. Sumner, divisions Richardson, Blenker, and Sedgwick.
3rd Corps. Brig.-Gen S.P. Heintzelman, divisions F.J. Porter, Hooker, and Hamilton.
4th Corps. Brig.-Gen. E.D. Keyes, divisions Couch, Smith, and Casey.
5th Corps. Maj-Gen. N.P. Banks, divisions Williams, and Shields.
The cavalry regiments attached to divisions, will, for the present remain so; subsequent orders will provide for those regiments, as well as for the reserve artillery, regular infantry, and regular cavalry.
Arrangements will be made to unite the divisions of each army corps, as promptly as possible. The commanders of the divisions, will at once report in person, or where that is impossible, by letter to the commander of their army corps.
By command of
A.V. Colburn, Ass’t. Adj’t. Gen’l.