United States Armies and Departments
in the Eastern Theater of the Civil War
July 1861

July 1-18

Department of the East

Major General John E. Wool

All of the United States east of the Mississippi not in other departments.

Dept. of Washington

Bde. General K. F. Mansfield

The District of Columbia, Alexandria County, Va., and Maryland as far as Bladensburg.

Dept. of Pennsylvania

Major General Robert Patterson

Pennsylvania, Delaware, and Maryland not in the Depts. of Washington and Annapolis.

Dept. of Annapolis

Major General Nathaniel Banks

Maryland between Annapolis, Baltimore and Washington.

Dept. of Virginia

Bde. General Benjamin F. Butler

An area 60 miles around Fortress Monroe

Dept. of N.E. Virginia

Bde. General Irvin McDowell

Virginia east of the Allegheny Mountains and north of the James River, except the Dept. of Virginia.

July 19-31

Department of the East

Major General John E. Wool

All of the United States east of the Mississippi not in other departments.

Dept. of Washington

Brigadier General Joseph K. F. Mansfield

Prince George, Montgomery, and Frederick Counties added; merged into the Military District of the Potomac 7/25.

Dept. of Pennsylvania

Major General Robert Patterson (to 7/27)

Major General John A. Dix (after 7/27)

Pennsylvania, Delaware, and Maryland not in the Depts. of Washington & Shenandoah.

Dept. of Annapolis

Renamed Dept. of Maryland 7/19.

Major General John A. Dix (7/19 -7/25)

Merged into Dept. of Pennsylvania 7/25.

Dept. of Virginia

Brigadier General Benjamin F. Butler

An area 60 miles around Fortress Monroe

Dept. of N.E. Virginia

Brigadier General Irvin McDowell

Merged into the Military District of the Potomac 7/25.

Dept. of the Shenandoah (est. 7/19)

Major General Nathaniel P. Banks

The Valley of Virginia, and Washington & Allegheny Counties in Maryland