< to July • August 1861

Commanded by Brigadier General Irvin McDowell

The Department was discontinued and merged into the Department of the Potomac on August 17, 1861

1st Division Brigadier General Daniel Tyler
First Brigade Colonel Erasmus Keyes
Second Brigade Brig. Gen. R. C. Schenck
Third Brigade Colonel William T. Sherman
Fourth Brigade Colonel Israel Richardson
2nd Division Colonel David Hunter
First Brigade Colonel Andrew Porter
Second Brigade Colonel Ambrose Burnside
3rd Division Colonel Samuel P. Heintzelman
First Brigade Colonel W. B. Franklin
Second Brigade Colonel J. H. H. Ward
Third Brigade Colonel Oliver O. Howard
4th Division Brigadier General Theodore Runyon
First Brigade
Second Brigade
5th Division Colonel Dixon S. Miles
First Brigade Colonel Louis Blenker
Second Brigade Colonel T. Davies