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Commanded by Major General George B. McClellan
On March 3, 1862, President Lincoln created the first five army corps in the Army of the Potomac and appointed their commanders. This was done despite the protests of General McClellan, who wanted to delay until he had judged his division commanders in battle.
| Headquarters | ||
| First Corps | Major General Irvin McDowell | |
| First Division | Brig. Gen. Willliam B. Franklin | |
| Second Division | Brig. Gen. George A. McCall | |
| Third Division | Brig. Gen. Rufus King | |
| Second Corps | Brigadier General Edwin V. Sumner | |
| First Division | Brig. Gen. Israel B. Richardson | |
| Second Division | Brig. Gen. John Sedgwick | |
| Blenker’s Division | Brig. Gen. Louis Blenker | transferred to Dept. Mountains 3/31 |
| Third Corps | Brigadier General Samuel P. Heintzelman | |
| First Division | Brig. Gen. Fitz John Porter | |
| Second Division | Brig. Gen. Joseph Hooker | |
| Third Division | Brig. Gen. C. S. Hamilton | |
| Fourth Corps | Brigadier General Erasmus Keyes | |
| First Division | Brig. Gen. Darius N. Couch | |
| Second Division | Brig. Gen. William F. Smith | |
| Third Division | Brig. Gen. Silas Casey | |
| Fifth Corps | Major General Nathaniel P. Banks | |
| First Division | Brig. Gen. Alpheus S. Williams | |
| Second Division | Brig. Gen. John Shields | |
| Cavalry Command | Brig. Gen. John P. Hatch | |
| Cavalry Reserve | Brigadier General Philip St. George Cooke | |
| First Brigade | Colonel William H. Emory | |
| Second Brigade | Colonel George A. H. Blake | |
| Artillery Reserve | Colonel Henry J. Hunt | |
| Military District of Washington | Brigadier General James Wadsworth | |