References:
Dyer's Compendium of the War of the Rebellion, 1959 Edition, Pages 254-257, Volume Unknown.

Commanding Armies of the United States

Winfield Scott, Brevet Lieutenant General. To November 6, 1861.
George B. McClellan, Major General. November 5, 1861, to March 11, 1862.
No General Commander from March 11 to July 11, 1862.
H. W. Halleck, Major General. July 11, 1862, to March 12, 1864.
Ulysses S. Grant, Lieutenant General. March 12, 1864, to March 4, 1869.

DEPARTMENT OF THE WEST

In existence at the beginning of the war. Merged into Western Department July 3, 1861.

Commanders:

W. S. Harney, Brigadier General. November 17, 1860, to May 31, 1861.
Nath'l Lyon, Brigadier General. May 31, 1861, to July 3, 1861.

DEPARTMENT OF THE EAST

In existence at the beginning of the war. Abolished August 17, 1861. Recreated January 3, 1863.

Commanders:

John E. Wool, Major General. To August 17, 1861.
John E. Wool, Major General. January 12, 1863, to July 18, 1863.
John A. Dix, Major General. July 18, 1863, to June 27, 1865.

DEPARTMENT OF FLORIDA

In existence at the beginning of the war. Merged into Department of the South, March 15, 1861.

Commanders:

Harvey Brown, Brevet Colonel U. S. A. Apr. 13, 1861, to February 22, 1862.
L. G. Arnold, Brigadier General. February 22. 1862, to March 15, 1862.

DEPARTMENT OF THE PACIFIC

In existence at the beginning of the war.

Commanders:

E. V. Sumner, Brigadier General. Apr. 25, 1861, to October 20, 1861.
Geo. Wright, Colonel U. S. A. October 20, 1861, to July 1, 1864.
Irvin McDowell, Major General. July 1, 1864, to June 27, 1865.

DEPARTMENT OF WASHINGTON

Constituted April 9, 1861, to consist of District of Columbia to its original boundaries, and the State of Maryland as far as Bladensburg. Merged into Military Division of the Potomac July 25, 1861. Recreated February 2, 1863.

Commanders:

C. F. Smith, Lieut. Colonel U. S. A. Apr. 10, 1861, to Apr. 28, 1861.
J. K. F. Mansfield, Colonel U. S. A. Apr. 28, 1861, to March 15, 1862.
S. P. Heintzelman, Major General. February 7. 1863, to October 14, 1863.
C.C. Augur, Major General. October 14, 1863, to June 27, 1865.

DEPARTMENT OF ANNAPOLIS

Constituted April 27, 1861, to include the Counties for 20 miles each side of the Railroad from Annapolis to the City of Washington, as far as Bladensburg. Changed to Dept. of Maryland, July 19, 1861, and merged into Dept. of Pennsylvania, July 25, 1861.

Commanders:

B. F. Butler, Brigadier General. Apr. 27, 1861, to May 15, 1861.
Geo. Cadwallader, Major General. May 15, 1861, to June 11, 1861.
N. P. Banks, Major General. June 11, 1861, to July 19, 1861.
John A. Dix, Major General. July 19, 1861, to July 25, 1861.

DEPARTMENT OF PENNSYLVANIA

Constituted April 27, 1861, to consist of Pennsylvania, Delaware, and all of Maryland not embraced in Departments of Annapolis and Washington. Merged into Department of the Potomac, August 24, 1861. Recreated December 1, 1864.

Commanders:

Robert Patterson, Major General. Apr. 29, 1861, to July 25, 1861.
John A. Dix, Major General. July 25, 1861, to August 24, 1861.
Geo. Cadwallader, Major General. December 1, 1864, to June 27, 1865.

DEPARTMENT OF THE OHIO

Constituted May 3, 1861, to consist of Ohio, Indiana, Illinois. Dept. extended to embrace West Virginia and Pennsylvania lying North of the Great Kanawha, North and West of the Greenbrier, etc. State of Missouri added to Department June 6, 1861. Illinois transferred to Western Dept. July 3 1861. Boundaries changed September 19, 1861, to consist of Ohio, Indiana, and so much of Kentucky as lies within 15 miles of Cincinnati, Ohio. State of Michigan added November 9, 1861. Also Kentucky, East of Cumberland River. Merged into Mountain Department and Dept. of Mississippi March 11, 1862. Recreated August 19, 1862, to consist of the States of Ohio, Michigan, Indiana, Illinois, Wisconsin, and Kentucky East of Tennessee River and including Cumberland Gap. Annexed to Department of the Cumberland January 17, 1865.

Commanders:

George B. McClellan, Major General. May 13, 1861, to July 23, 1861.
W S. Rosecrans, Brigadier General. July 23, 1861, to September 21, 1881.
O M. Mitchell, Brigadier General. September 21. 1861, to November 15, 1861.
Don Carlos Buell, Brigadier General. November 15, 1861, to March 11, 1862.
H G. Wright, Major General. August 25, 1862, to March 25, 1863.
A E. Burnside, Major General. March 25, 1863, to December 11, 1863.
J. G. Foster, Major General. December 11, 1863, to Feby. 9, 1864.
J M Schofleld, Major General. February 9, 1864, to November 17, 1864.
Geo. Stoneman, Major General. November 17, 1864, to January 17, 1865.

DEPARTMENT OF VIRGINIA

Created May, 1861. Merged into Dept. of Virginia and North Carolina July 15. 1863. Recreated January 31, 1865. (Also known as Army of the James from January 31, 1865.)

Commanders:

B. F Butler, Major General. May 22, 1861, to August 17, 1861.
John E Wool, Major General. August 17, 1861, to June 17, 1862.
John A. Dix, Major General. .June 17, 1862, to July 15, 1863.
E.O.C. Ord, Major General. January 31, 1865, to May .., 1865.
A. H. Terry, Major General. May .., 1865, to June 27, 1865.

DEPARTMENT OF NORTHEAST VIRGINIA

Constituted May 27, 1861, to consist of that part of Virginia East of the Allegheny Mountains and North of James River, except Fort Monroe and 60 miles around the same. Merged into Department of the Potomac July 25, 1861.

Commanders:

Irvin McDowell, Major General. May 27, 1861, to July 25, 1861.

DEPARTMENT OF KENTUCKY

Created May 28, 1861, to consist of the State of Kentucky lying within 100 miles of the Ohio River. Merged into the Dept. of the Cumberland August 15, 1861. Recreated February 10, 1865.

Commanders:

Robert Anderson, Colonel U.S.A. May 28, 1861, to August 15, 1861.
J. M. Palmer, Major General. February 18, 1865, to June 27, 1865.

WESTERN DEPARTMENT

Constituted July 3, 1861, to consist of the States of Illinois, and States and Territories West of the Mississippi River and on this side of the Rocky Mountains, including New Mexico. Merged into Department of Missouri and Kansas November 9, 1861.

Commanders:

John C. Fremont, Major General. July 25, 1861, to November 2, 1861.
David Hunter, Major General. November 2, 1861, to November 9, 1861.

DEPARTMENT OF THE SHENANDOAH

Constituted July 19, 1861, to consist of the Valley of Virginia, Counties of Washington and Alleghany in Maryland, and such parts of Virginia as may be covered by the Army in its operations. Merged into the Department of the Potomac August 17, 1861. Recreated April 4, 1862. Merged into Army of Virginia June 26, 1862.

Commanders:

N. P. Banks, Major General. July 25, 1861, to August 17, 1861.
N. P. Banks, Major General. Apr. 4, 1862, to June 26, 1862.

MILITARY DISTRICT OF THE POTOMAC

Constituted July 25, 1861, by consolidation of the Department of Washington and the Department of Northeast Virginia. Changed to Department or Army of the Potomac August 15, 1861.

Commanders:

Geo. B. McClellan, Major General. July 25, 1861, to August 15, 1861.

DEPARTMENT, OR ARMY OF THE POTOMAC

Created August 15, 1861, from Military District of the Potomac.

Commanders:

Geo. B. McClellan, Major General. August 15, 1861, to November 9, 1862.
A. E. Burnside, Major General. November 9, 1862, to January 26, 1863.
Joseph Hooker, Major General. January 26, 1863, to June 28, 1863.
Geo. G. Meade, Major General. June 28, 1863, to December 30, 1864.
John G. Parke, Major General. December 30, 1864, to January 11, 1865.
Geo. G. Meade, Major General. January 11, 1865, to June 27, 1865.

DEPARTMENT OF THE CUMBERLAND

Constituted August 15, 1861, to consist of the States of Kentucky and Tennessee. Merged into Departments of Missouri and Ohio November 9, 1861. Recreated October 24, 1862, to consist of Tennessee East of the Tennessee River, and such parts of Alabama and Georgia as may be taken possession of by United States forces.

Commanders:

Robert Anderson, Brigadier General. Sept 24, 1861, to Oct 8, 1861.
W. T. Sherman, Brigadier General. October 8, 1861, to November 9, 1861.
W. S. Rosecrans, Major General. October 30, 1862, to October 20, 1863.
Geo. H. Thomas, Major General. October 20, 1863, to June 27, 1865.

DEPARTMENT OF NEW ENGLAND

Created Oct 1, 1861, consisting of the Six New England States. Discontinued February 20, 1862.

Commanders:

B. F. Butler, Major General. Oct 1, 1861, to February 20, 1862.

DEPARTMENT OF WESTERN VIRGINIA

Organized October 11, 1861, from Department of the Ohio. Merged into Mountain Department March 11, 1862.

Commanders:

W. S. Rosecrans, Brigadier General. October 11, 1861, to March 11, 1862.

DEPARTMENT OF NEW YORK

Organized October, 1861. Merged into Department of the East January 3, 1863.

Commanders:

E. D. Morgan, Major General. October 26, 1861, to January 3, 1863.

DEPARTMENT OF NEW MEXICO

Created November 9, 1861, to consist of the Territory of New Mexico.

Commanders:

W. W. Loring, Colonel U. S. A. March 23, 1861, to June 16, 1861.
E. R. S. Canby, Bvt Lieut-Col. U. S. A. .June 16, 1861, to June 22, 1861.
James H. Carleton, Brigadier General. Sept 18, 1862, to June 27, 1865.

DEPARTMENT OF KANSAS

Created November 9, 1861, to consist of the State of Kansas, the Indian Territory West of Arkansas, and the Territories of Nebraska, Colorado and Dakota. Merged into the Department of Mississippi March 11, 1862. Recreated May 2, 1862. Merged into the Department of Missouri, Sept 19, 1862. Recreated January 1, 1864. Merged into the Department of Missouri, January 3, 1865.

Commanders:

David Hunter, Major General. November 20, 1861, to March 11, 1862.
J. G. Blunt, Brigadier General. May 5, 1862, to Sept 19, 1862.
S. R. Curtis, Major General. January 16, 1864, to January 30, 1865.

DEPARTMENT OF MISSOURI

Created November 9, 1861, to consist of the States of Missouri, Iowa, Minnesota, Wisconsin, Arkansas, and that portion of Kentucky West of the Cumberland River. Merged into Department of Mississippi March 11, 1862. Recreated September 19, 1862, to consist of Missouri, Arkansas, Kansas, and bordering Indian Territory. Colorado and Nebraska Territories added October 11, 1862.

Commanders:

H. W. Halleck, Major General. November 19, 1861, to March 11, 1862.
S. R. Curtis, Major General. September 24, 1862, to May 24, 1863.
J. M. Schofleld, Major General. May 24, 1863, to January 30, 1864.
W. S. Rosecrans, Major General. January 30, 1864, to December 9, 1864.
G. M. Dodge, Major General. December 9, 1864, to June 27, 1865.

DEPARTMENT OF NORTH CAROLINA

Created January 7, 1862, to consist of the State of North Carolina. Merged into Department of Virginia and North Carolina July 15, 1863. Recreated January 31, 1865.

Commanders:

A. E. Burnside, Brigadier General. January 13, 1862, to July 10, 1862.
J. G. Foster, Major General. July 10, 1862, to July 15, 1863.
J. M. Schofield, Major General. January 31, 1865, to June 27, 1865.

DEPARTMENT OF KEY WEST

Created February 1862. Merged into Department of the South March 15, 1862.

Commanders:

J. M. Brannan, Brigadier General. February 21, 1862, to March 15, 1862.

DEPARTMENT OF THE GULF

Constituted February 23, 1S62. To comprise all of the Coast of the Gulf of Mexico west of Pensacola Harbor, and so much of Gulf States as may be occupied by U. S. forces. West Florida added August 8, 1862.

Commanders:

B. F. Butler, Major General. March 20, 1862, to December 17 1862
N. P. Banks, Major General. December 17, 1862 to September 23 1864
S A. Hurlbut, Major General. September 23, 1864, to April 22 1865.
N. P. Banks, Major General. April 22, 1865, to June 3 1865
E. R. S. Canby, Major General. June 3, 1865, to June 27, 1865.

MOUNTAIN DEPARTMENT

Created March 11, 1862, from Department of Western Virginia. Merged into Army of Virginia, June 26, 1862.

Commanders:

W. S. Rosecrans, Brigadier General. March 14, 1862. to March 29, 1862.
J. C Fremont, Major General. March 29, 1862, to June 26, 1862.

DEPARTMENT OF MISSISSIPPI

Created March 15, 1862, from Departments of Missouri, Ohio and Kansas. Me ged into Dept. of Missouri September 19 1S62. Recreated November 28, 1864.

Commanders:

H. W Halleck Major General. March 13, 1862, to September 19, 1862.
N. J. T. Dana, Major General. December 8, 1864, to May 14, 1865.
G. K. Warren, Major General. May 14, 1S65, to June 24, 1865.
H. W. Slocum, Major General. June 24, 1865, to June 27, 1865.

DEPARTMENT OF THE SOUTH

Created March 15. 1862. To consist of States of South Carolina, Georgia and Florida. Dept. of Key West added March 15, 1862. West Florida detached August 8, 1862, and annexed to Dept. of the Gulf.

Commanders:

David Hunter, Major General. March 21, 1862, to September 5, 1862.
J M. Brannan, Brigadier General. September 5, 1862, to September 17, 1862.
O. M. Mitchell, Major General. September 17, 1862, to October 27, 1862.
J. M Brannan, Brigadier General. Oct 27, 1862, to January 20, 1863.
David Hunter, Major General. January 20, 1863, to June 12, 1863.
Q A Gilmore, Brigadier General. June 12, 1863, to May 1, 1864.
J. P. Hatch, Brigadier General. May 1, 1864, to May 26, 1864.
J. G. Foster, Major General. May 26, 1864, to February 9. 1865.
Q. A. Gilmore, Major General. February 9, 1865, to June 28, 1865.

MIDDLE DEPARTMENT

Constituted March 22, 1862. To consist of States of New Jersey, Pennsylvania, Delaware, The Eastern Shore of Maryland and Virginia and the Counties of Cecil, Harford, Baltimore and Ann Arundel. Md.

Commanders:

John A. Dix, Major General. March 22, 1862, to June 9, 1862.
John E Wool, Major General. June 9, 1862, to December 22, 1862.
R. C. Schenck, Major General. December 22,. 1862, to August 10, 1863.
W. W. Morris, Bvt. Brig. General. Aug, 10, 1863, to August 31, 1863.
R. C. Schenck, Major General. August 31, 1863, to September 28, 1863.
E. B. Tyler, Brigadier General. September 23, 1S63, to October 10, 1S63.
R . C. Schenck, Major General. October 10, 1863, to December 5. 1863.
H H. Lockwood, Brigadier General. December 5, 1863, to March 22, 1864.
Lew Wallace, Major General. March 22, 1864, to February 1, 1865.
W. W. Morris, Bvt. Brig. General. February 1, 1805, to Apr. 19, 1865.
Lew Wallace, Major General. Apr. 19, 1865, to June 27, 1865.

DEPARTMENT OF THE RAPPAHANNOCK

Constituted April 4, 1862, to consist of that portion of Virginia East of the Blue Ridge and West of the Potomac, and the Fredericksburg and Richmond, R R. including the District of Columbia and the country between the Potomac and the Patuxent. Merged into the Army of Virginia June 26, 1862.

Commanders:

Irvin McDowell, Brigadier General. Apr. 4, 1862, to June 26, 1862.

ARMY OF VIRGINIA

Constituted June 26, 1862, to consist of the forces under Major General Fremont, Mountain Dept Major General Banks, Dept. of the Shenandoah and Major General McDowell. Dept. of the Rappahannock, and including the forces at Washington, D. C, under Brigadier General Sturgis. Merged into Army of the Potomac September 2, 1862.

Commanders:

John Pope, Major General. June 26, 1862, to September 2, 1862.

DEPARTMENT OF THE NORTHWEST

Constituted September 6, 1862, to consist of the States of Wisconsin, Iowa. Minnesota and Territories of Nebraska and Dakota.

Commanders:

John Pope, Major General. September 16, 1862, to November 28, 1862.
W. L. Elliott, Brigadier General. November 28, 1862, to February 18, 1863.
John Pope, Major General. February 13, 1863, to February 13, 1865.
S. R. Curtis, Major General. February 13, 1865, to June 27, 1865.

DEPARTMENT AND ARMY OF THE TENNESSEE

Created October 16, 1862, to include Cairo, Fort Henry and Fort Donelson, Northern Mississippi and portions of Kentucky and Tennessee West of the Tennessee River.

Commanders:

U S Grant, Major General. October 25, 1862, to October 24, 1863.
W. T. Sherman, Major General. October 24, 1863, to March 26, 1864.
J. B. McPherson, Major General. March 26, 1S64, to July 22. 1864.
John A. Logan, Major General. July 22, 1864, to July 27, 1864.
O O Howard, Major General. July 27, 1864, to May 19, 1865.
John A. Logan, Major General. May 19, 1865, to August 1, 1865.

DEPARTMENT OF THE MONONGAHEDA

Created June 9, 1863, to consist of that portion of Pennsylvania West of Johnstown and the Laurel Hill range of mountains, and the Counties of Hancock, Brooke and Ohio in the State of West Virginia, and Counties of Columbiana, Jefferson and Belmont in the State of Ohio Merged into Dept. of the Susquehanna April 6, 1864.

Commanders:

W. T. H. Brooks, Major General. June 11, 1863, to Apr. 6, 1864.

DEPARTMENT OF WEST VIRGINIA

Formed June, 1863.

Commanders:

B. F. Kelly, Brigadier General. June 28, 1863, to March 10, 1864.
F. Sigel Major General. March 10, 1864, to May 21, 1864.
David Hunter, Major General. May 21, 1864, to August 9, 1864
George Crook, Major General. August 9, 1864, to February 22, 1865
J. D. Stevenson, Brigadier General. February 22, 1865, to February 28 1865
W.S. Hancock, major General February 28, 1865, to March 1,l865.
S.S. Carroll, Bvt. Major General. March 1, 1865, to March 7 1865
W. S. Hancock, Major General. March 7, 1865, to March 20, 1865.
Geo. Crook, Major General. March 20, 1865, to March 22, 1865.
W. S. Hancock, Major General. March 22, 1865, to June 27, 1865.

DEPARTMENT OF THE SUSQUEHANNA

Created June 9, 1863, to consist of that portion of Pennsylvania East of Johnstown and the Laurel Hill Range of Mountains. Changed to Dept. of Pennsylvania December 1, 1864.

Commanders:

D. N. Couch, Major General. June 11, 1863, to December 1, 1864.

DEPARTMENT OF VIRGINIA AND NORTH CAROLINA (ARMY OF THE JAMES.)

Created July 15, 1863, by consolidation of the Departments of Virginia and North Carolina. Organized into Army of the James April 1864. Departments separated January 31, 1865, under their respective names.

Commanders:

J.G. Foster, Major General. July 18, 1863. to November 11, 1863.
B. F. Butler Major General. November 11, 1863, to August 27, 1864.
E.O.C Ord, Major General. August 27, 1864, to September 7, 1864.
B. F. Butler, Major General. September 7, 1864, to December 14, 1864
E.O.C. Ord, Major General. December 14, 1864, to December 24, 1864.
B. F. Butler, Major General. December 24, 1884, to January 8, 1865
E.O.C. Ord, Major General. January 8, 1865, to January 31, 1865.

MILITARY DIVISION OF THE MISSISSIPPI

Created Oct 18, 1863. Composed of Department of the Ohio Department of the Tennessee, Department of the Cumberland, and Arkansas. Department of Arkansas transferred to Military Division of West Mississippi May 7, 1864.

Commanders:

Ulysses S. Grant, Major General. October 18, 1863, to March 18, 1864
W. T. Sherman, Major General. March 18, 1864, to June 27, 1865.

NORTHERN DEPARTMENT

Constituted January 12, 1864, to consist of the States of Michigan, Ohio, Indiana and Illinois.

Commanders:

S. P. Heintzelman, Major General. January 20, 1864, to October 1. 1864.
Joseph Hooker, Major General. October 1, 1864, to June 27, 1865.

DEPARTMENT OF ARKANSAS

Created January 6, 1864, to consist of Arkansas except Fort Smith. Fort Smith and Indian Territory added April 17. 1864. Embraced in Military Division West Mississippi May 7, 1864.

Commanders:

Frederick Steele, Major General. January 30, 1864, to December 22 1864.
J. J. Reynolds, Major General. December 22, 1864, to August .., 1865.

MILITARY DIVISION OF WEST MISSISSIPPI

Created May 7, 1864, to consist of the Department of Arkansas and Department of the Gulf. Arkansas transferred to Military Division of Missouri March 21, 1865. Discontinued May 1865.

Commanders:

E. R. S. Canby, Major General. May 11, 1864, to May, 1865.

MIDDLE MILITARY DIVISION

Created August 6, 1864.

Commanders:

P. H. Sheridan, Major General. August 6, 1864, to February 27, 1865.
W. S. Hancock, Major General. February 27, 1864, to June 27, 1865.

ARMY OF GEORGIA

Constituted March 28, 1865. To consist of the 14th and 20th Army Corps

Commanders:

H. W. Slocum, Major General. March 28, 1865, to June 1, 1865.

MILITARY DIVISION OF THE JAMES

Created April 19, 1865, to consist of the Dept. of Virginia, and such parts of North Carolina as are not occupied by the command of Gen. W. T. Sherman.

Commanders:

H. W. Halleck. Major General. Apr. 19, 1865, to June 27, 1865.