The Fifty-first Infantry Illinois Volunteers was organized at Camp Douglas, Chicago, Illinois, December 24, 1861, by Colonel Gilbert W. Cumming.

February 14, 1862, ordered to Cairo, Illinois. Moved to Camp Cullum, on the Kentucky shore, on the 27th. On the 4th of March moved to Bertrand, Missouri, and on the 7th moved to Sykeston, and to New Madrid, and 10th, assigned to the Division of Brigadier General E. A. Paine, and Second Brigade, consisting of Twenty-second Illinois Infantry, and Fifty-first, Colonel Cumming commanding. On the 13th, made a reconnaissance in force, and, 14th, New Madrid was evacuated by the enemy.

April 7, moved against Island No. 10; 8th, pursued the enemy, compelling the surrender of General Mackall, and 4,000 prisoners; 9th, returned to New Madrid; 11th, embarked and proceeded down Mississippi to Osceola, Arkansas; 17th, moved toward Hamburg Landing, Tennessee, disembarking 22d. April 24, the Brigade of Brigadier General John M. Palmer, Twenty-second, Twenty-seventh, Forty-second and Fifty-first Illinois, and Company C, First Illinois Artillery, Captain Hightailing, known as the "Illinois Brigade," was assigned to Brigadier General Paine's Division. Engaged in the battle at Farmington, and siege of Corinth.

Just previous to the evacuation of Corinth, the Army of the Mississippi was organized into two wings and centre. The Division of Paine and Stanley, constituting Right Wing, under Brigadier General W. S. Rosecrans.

June 4, advanced near Baldwin, Mississippi, and fell back to Booneville. Colonel F. A. Harrington, Twenty-seventh Illinois, took command of the Brigade. On the 11th, moved from Booneville, and again encamped at Corinth, 14th; 28th, General Pope being transferred to Virginia, General Rosecrans assumed command of the Army of the Mississippi, and Brigadier General David S. Stanley, of Right Wing. July 9, army organized into five Divisions, under Brigadier Generals Paine, Stanley, Schuyler, Hamilton, Jeff C. Davis and Asboth, the Fifty-first being in First Brigade, First Division.

July 20, the division left Big Spring, and marched to Tuscumbia, Alabama. The Regiment was assigned to guard the railroad from Hillsboro to Decatur. August 24, Regiment concentrated at Decatur. September 4, crossed the Tennessee River, and moved via Athens, Alabama, to Nashville, Tennessee. Here the Division of Negley and Palmer remained as garrison, while the army moved to Louisville, under Buell. November 6, engaged in repelling the attack of Breckinridge, Morgan and Forrest. From September 11 to November 6, Nashville was cut off from communication with the North, the troops being on half rations. September 30, Colonel Cumming having resigned, Lieutenant Colonel Bradley was commissioned Colonel.

December 10, the Brigade was transferred to the Division of Brigadier General Phillip H. Sheridan, and designated as Third Brigade, Third Division, Right Wing, Fourteenth Army Corps, and marched 7 miles on Nolensville pike. December 26, moved against the enemy, under Bragg. December 30, the Brigade met the enemy and was engaged during the day, losing 7 wounded. December 31, the Regiment was in the thickest of the fight at Stone River, losing 57 killed, wounded and prisoners. The Division lost its three Brigade commands, Colonel Harrington being wounded and taken prisoner, and died a few days afterward. Colonel Bradley took command of the Brigade, and Major Davis of the Regiment, and upon Major Davis being wounded and carried from the field, Captain H. F. Wescott took command. On the 6th, moved 3 miles south of Murfreesboro, and encamped.

January, 1863, the wings and centre of the army were designated as Fourteenth, Twentieth and Twenty-first Army Corps, that of McCook being Twentieth Army Corps.

March 4, moved to Eagleville--Captain John G. McWilliams commanding Regiment. On the 8th, moved to Spring Hill; 10th, reached Duck Creek; 11th, Van Dorn crossed Duck River, on pontoons, and Granger returned to Franklin.

June 24, Twentieth Corps moved down the Shelbyville pike; 27th, marched to Beach's Grove. July 1, enter Tullahoma, which had been evacuated the night before. Joined in pursuit of the enemy to Elk River, Winchester and Cowan, Bragg retreating over the Cumberland mountains, and across the Tennessee River. Remained at Cowan until the 9th, then ascending the mountains, encamped on the summit on the site of "Southern University." July 30, moved to Bridgeport, Alabama. September 2, crossed Tennessee River, and moved to foot of Sand Mountain. September 4, ascended the mountain; 5th, moved to Trenton, Georgia; 6th and 7th, marched down to Lookout Valley; 10th, to Winston's Gap; 11th, Alpine, Georgia; 14th, marched up Lookout Valley; 15th, from Stevens' Gap to McElmore's Cove.

After some days' movements, entered the battle of Chickamauga, at 4 p.m.; 19th, losing that evening, 90 men out of 209 engaged. During the night erected barricades. On the 20th, went into position on extreme right: by noon were heavily engaged, and in the afternoon the whole Division fell back, in confusion, to Mission Ridge; 21st, threw up works at Rossville; 22d, crossed Chickamauga Creek.

October 10, the Twentieth and Twenty-first Corps being consolidated, formed Fourth Corps, under Major General Gordon Granger. Regiment being in Third Brigade, Colonel C. G. Harker; Second Division, Major General Sheridan.

November 24, at Mission Ridge, was engaged, losing 39 out of 150 men engaged, including Major Davis wounded, and Captain George L. Billows killed. Captain A. M. Tilton commanding Regiment.

November 28, 1863, marched to the relief of General Burnside at Knoxville. December 16, moved, by rail, to Blain's Cross Roads. January 9, 1864, Colonel Bradley returned. January 15, moved toward Chattanooga. February 10, Regiment mustered as veterans, and started for Chicago, where, 17th, the men received veteran furlough.

Regiment left for the front March 28, 1864, via Louisville, Nashville and Chattanooga, to Cleveland, Tennessee. May 3, commenced the Atlanta campaign.

Was engaged at Rocky Face Ridge, May 9, losing two men wounded. Resaca, 14th, losing Captain Lester killed, and 20 men wounded. At Dallas, May 25, found the enemy in position, and were engaged 11 days, losing one officer, and 11 men wounded. June 15, in a skirmish, lost Captain Tilton wounded, and 12 killed and wounded.

Engaged at Kenesaw Mountain and in the assault of June 27, losing 2 officers wounded and 54 men killed and wounded, and Adjutant Henry W. Hall and Lieutenant A. V. McCormack killed.

July 4, 1864, moved to Chattahoochie River. Marched to Rosewell and crossed, returning to the Corps 13th. July 20, engaged at Peach Tree Creek. Casualties, 5 wounded. Was engaged, during siege of Atlanta, in the skirmish of Jonesboro, losing two wounded, and at Lovejoy, losing three wounded. Marched into Atlanta, 8th September. During the whole campaign the Regiment lost 3 officers killed, 4 wounded, and 105 men killed and wounded.

September 28, moved to Chattanooga, and thence to Bridgeport, Alabama. October 18, moved to Chattanooga. Here 192 drafted men joined the Regiment. Here, too, Chaplain Raymond, a venerable and good man, resigned.

Moved to Alpine, Georgia; from thence, via Chattanooga, Athens, Alabama, to Pulaski, Tennessee. November 22, marched to Lynnville; 24th, to Columbia; 29th, retreated to Spring Hill, at which place the enemy made an attack. The Regiment lost 12 wounded, including Captain George I. Waterman, A. A. A. G., and General Bradley.

November 30, moved to Franklin, and was heavily engaged in the battle of Franklin, losing Lieutenant Thomas, killed, Captain Tilton and Lieutenants Johnson and Hills, wounded, 52 men killed and wounded, and 98 missing.

December 1, reached Nashville. Engaged in the battle of Nashville, December 15 and 16, losing 1 man killed and 5 wounded. After the battle pursued the flying enemy, and afterward moved to Huntsville, Alabama.

March 31, 1865, moved to Greenville, East Tennessee. April 15, moved to Nashville. April 11, Company I - 90 men - joined the Regiment from Camp Butler.

June 15, Company F, Lieutenant James Skidmore commanding, was mustered out of service: 16th, moved to Johnsonville, Tennessee, and embarked for New Orleans, Louisiana. July 28, embarked for Texas; 31st, disembarked at Port Lavaca. August 1, moved to Camp Placidor, Texas.

Mustered out September 25, 1865, at Camp Irwin, Texas, and arrived at Camp Butler, Illinois, October 15, 1865, for final payment and discharge.