ORGANIZATION OF THE UNION AND CONFEDERATE ARMIES AT CHICKAMAUGA
UNION
The Army of the Cumberland (Union) commanded by Maj. Gen. William S. Rosecrans, consisted of the following:
| 14th Army Corps | Maj. Gen. George H. Thomas |
| 20th Army Corps | Maj. Gen. Alexander McD. McCook |
| 21st Army Corps | Maj. Gen. Thomas L. Crittenden |
| Cavalry Corps | Brig. Gen. Robert B. Mitchell |
| Reserve Corps | Maj. Gen. Gordon Granger |
Thomas had 4 divisions, commanded by Baird, Negley, Brannan and Reynolds.
Baird had 3 brigades, commanded by Scribner, Starkweather and John H. King.
Negley had 3 brigades, commanded by John Beatty, Stanley and Sirwell.
Brannan had 3 brigades, commanded by Connell, Croxton and Van Derveer.
Reynolds had 3 brigades, commanded by Wilder, Edward A. King and Turchin.
McCook had 3 divisions, commanded by Jefferson C. Davis, Richard W. Johnson and Sheridan.