Commanded by Major General George B. McClellan
| Headquarters and Escorts | ||
| 1st Army Corps | Major Genera Joseph Hooker (w) Brigadier General George G. Meade |
|
| 1st Division | Brigadier General Abner Doubleday (1) | |
| 2nd Division |
Brigadier General James B. Ricketts | |
| 3rd Division | Brigadier General George G. Meade (^) Brigadier General Truman Seymour |
|
| 2nd New York Cavalry (Companies A,B,I & K) |
Captain John E. Naylor | |
| 15th Pennsylvania Cavalry (det.) | Colonel William J. Palmer | |
| 2nd Army Corps | Major General Edwin V. Sumner | |
| 1st Division | Major General Israel B. Richardson (mw) Brigadier General Winfield S. Hancock |
|
| 2nd Division | Major General John Sedgwick (w) Brigadier General Oliver O. Howard |
|
| 3rd Division | Major General William H. French | |
| 6th New York Cavalry, Company D | Captain Henry W. Lyon | |
| 6th New York Cavalry, Company K | Captain Riley Johnson | |
| 5th Army Corps | Major General Fitz John Porter | |
| 1st Division | Major General George W. Morell | |
| 2nd Division | Brigadier General George Sykes | |
| 3rd Division (2) | Brigadier General Andrew A. Humphreys | |
| Artillery Reserve | Lieutenant Colonel William Hays | |
| 1st Maine Cavalry (det.) | Captain George J. Summat | |
| 6th Army Corps | Major General William B. Franklin | |
| 1st Division | Major General Henry W. Slocum | |
| 2nd Division |
Major General William F. Smith | |
| 4th Army Corps, 1st Division (3) | Major General Darius Couch | |
| 6th Pennsylvania Cavalry, Companies B & G |
Capt H. P. Muirheid | |
| 9th Army Corps | Major General Ambrose E. Burnside (4) Brigadier General Jacob D. Cox |
|
| 1st Division | Brigadier General Orlando B. Wilcox | |
| 2nd Division |
Brigadier General Samuel D. Sturgis | |
| 3rd Division | Brigadier General Isaac P. Rodman (mw) Colonel Edward Harland |
|
| Kanawha Division | Brigadier General Jacob D. Cox (^) Colonel Eliakim P. Scammon |
|
| 6th New York Cavalry (8 companies) | Colonel Thomas V. Devin | |
| 3rd Company Ohio Cavalry | Lieutenant Jonas Seamen | |
| 3rd United States Artillery, Batteries L&M | Captain John Edwards, Jr. | |
| 1st Maine Cavalry, Company G | Captain Zebulon B. Blethen | |
| 12th Army Corps | Major General Joseph K. F. Mansfield (mw) Brigadier General Alpheus S. Williams |
|
| 1st Division | Brigadier General Alpheus S. Williams (^) Brigadier General Samuel W. Crawford (w) Brigadier General George H.Gordon |
|
| 2nd Division |
Brigadier General George S. Greene | |
| Artillery Reserve | Captain Clermont L. Best | |
| 1st Michigan Cavalry, Company L | Captain Melvin Brewer | |
| Cavalry Division | Brigadier General Alfred Pleasonton |
Key to notes:
(k) = killed, (w) = wounded, (mw) = mortally wounded, (c) = captured (^) = took over parent unit
Links for regiments, batteries, companies, and individuals go to unit histories or biographies on www.civilwarintheeast.com
Notes:
(1) Brigadier General John P. Hatch was wounded at South Mountain on 9/14
(2) Reached the battlefield 9/18
(3) Attached to 6th Corps. Not on the battlefield 9/17
(4) In temporary command of army’s Left Wing, which included the 5th Corps as well as his own 9th Corps. Continued to act as wing commander even after 5th Corps was removed from his control.