Organized in Cincinnati under Col. Robert M. McCook. The members of the regiment were primarily of German descent. The 9th was mustered into three months service April 22nd, 1861 and reorganized into three years service May 28th 1861. It served in West Virginia under McClellan and transferred to the Army of the Potomac, July 27th, and to the Army of the Ohio, in December. The 9th did valuable service in Tennessee, and participated in the battle of Chickamauga, with heavy loss. It took part in the battle of Mission Ridge and was at the battle of Resaca during Sherman's Atlanta campaign. The Regiment's service having expired, it returned to Camp Dennison and was mustered out, June 7th, 1864.
From Dyer's Compendium
9th Regiment Infantry (3 Months). Organized at Camp Harrison near Cincinnati, Ohio, April 22, 1861. Moved to Camp Dennison, Ohio, and duty there till May 27. Reorganized at Camp Dennison for three years May 27 to June 13, 1861, the first three-years Regiment from the State. Three months' men mustered out August 4, 1861.
9th Regiment Infantry (3 Years). Organized at Camp Dennison, Ohio, May 27 to June 13, 1861. Ordered to West Virginia June 16. Attached to 3rd Brigade, Army of Occupation, W. Va., to August, 1861. 2nd Brigade, Kanawha Division West Virginia, to November, 1861. 3rd Brigade, Army Ohio, to December, 1861. 3rd Brigade, 1st Division, Army Ohio, to September, 1862. 3rd Brigade, 1st Division, 3rd Corps, Army Ohio, to November, 1862. 3rd Brigade, 3rd Division, Center 14th Army Corps, Army of the Cumberland, to January, 1863. 3rd Brigade, 3rd Division, 14th Army Corps, to October, 1863. 2nd Brigade, 3rd Division, 14th Army Corps, to May, 1864.
SERVICE.--West Virginia Campaign July 6-17, 1861. Battle of Rich Mountain July 10. Capture of Beverly July 12. Duty at New Creek till August 27. At New River till November 24. Moved to Louisville, Ky., November 24-December 2, thence to Lebanon, Ky., and duty there till January, 1862. Advance to Camp Hamilton January 1-17. Battle of Mill Springs January 19-20. March to Louisville, Ky., thence moved to Nashville, Tenn, via Ohio and Cumberland Rivers February 10-March 2. March to Pittsburg Landing, Tenn., March 20-April 7. (Presented by ladies of Louisville with a National flag for gallantry at Mill Springs.) Advance on and siege of Corinth, Miss., April 29-May 30. Ordered to Tuscumbia, Ala., June 22, and duty there till July 27. Moved to Decherd, Tenn., July 27, thence march to Louisville, Ky., in pursuit of Bragg August 21-September 26. Pursuit of Hood into Kentucky October 1-15. Battle of Perryville, Ky., October 8. March to Nashville, Tenn., via Bowling Green, Lancaster, Danville and Lebanon October 16-November 7. Duty at South Tunnel opening communications with Nashville November 8 26. Guard fords of the Cumberland till January 14. 1863. Duty at Nashville, Tenn., January 15-March 6. Expedition toward Columbia March 6-14. Moved to Triune and duty there till June. Franklin June 4-5. Middle Tennessee or Tullahoma Campaign June 23-July 27. Occupation of Middle Tennessee till August 16. Passage of the Cumberland Mountains and Tennessee River and Chickamauga (Ga.) Campaign August 16-September 22. Battle of Chickamauga, Ga., September 19-21. Siege of Chattanooga, Tenn., September 24-November 23. Reopening Tennessee River October 26-29. Brown's Ferry October 27, Chattanooga-Ringgold Campaign November 23-27. Battles of Orchard Knob November 23. Mission Ridge November 24-25. Demonstration on Dalton, Ga., February 22-27, 1864. Tunnel Hill, Buzzard's Roost Gap and Rocky Face Ridge February 23-25. Reconnoissance from Ringgold toward Tunnel Hill April 29. Atlanta (Ga.) Campaign May 1-25. Demonstration on Rocky Faced Ridge May 8-11. Battle of Resaca May 14-15. Advance on Dallas May 18-25. Left front May 25. Mustered out at Camp Dennison, Ohio, June 7, 1864, expiration of term. Regiment lost during service 6 Officers and 85 Enlisted men killed and mortally wounded and 2 Officers and 60 Enlisted men by disease. Total 153.