The following is taken from New York in the War of the Rebellion, 3rd ed. Frederick Phisterer. Albany: J. B. Lyon Company, 1912.

June 17, 1863, Col. W. B. Tibbits received authority to recruit this regiment. The companies were mustered in the service of the United States for three years, at Troy, where the regiment was organized. A, B, C and D August 28; E and F September I and 18, respectively; G October 14, H and I October 15, and K, L and M in November, December, 1863, and January, 1864. September 9, 1865, the regiment was consolidated into a battalion of seven companies, A to G; Company H being transferred to Company F, I to D, K to E, L to F, and M to E.

The companies were recruited principally: A, E, H and I at Troy; B at Troy, Ithaca, Elmira and Oswego; C, G and K at Rochester and Troy; D at Troy and Oswego; F at Troy, Cohoes and Watervliet; L at Rochester; and M at Ithaca, Enfield, Dryden and Groton.

Five companies left the State September 4, 1863; one September 19; three, October 19, 1863; one in November, 1863; the remainder in February, 1864; and the regiment served in the Department of Washington, D. C., 22d Corps, from September, 1863; in the 1st Brigade, 1st Division, Cavalry, Army of West Virginia, from January, 1864; at Remount Camp, Md., from latter part of August to close of October, 1864; in the Army of the Shenandoah from October, 1864; in the 1st Brigade, 2d Division, Cavalry, A. S., from November, 1864; in the Department of West Virginia, from March, 1865; at Washington, D. C. from May, 1865; at Denver city, Col., Department of Missouri, from September, 1865.

The regiment (seven companies), under the command of Col. Charles Fitzsimmons, was honorably discharged and mustered out at Denver city, Col., Company B June 23, F June 26, G June 29, C, E and D July 3, 5 and 7, respectively; and at Fort Leaven-worth, Kans., Company A, August 31, 1866.

It lost during its service by death, killed in action, 2 officers, 40 enlisted men; of wounds received in action, I officer, 23 enlisted men; of disease and other causes, I officer, 78 enlisted men; total, 4 officers, 141 enlisted men; aggregate, 145; of whom 19 enlisted men died in the hands of the enemy.

The following is taken from The Union army: a history of military affairs in the loyal states, 1861-65 -- records of the regiments in the Union army -- cyclopedia of battles -- memoirs of commanders and soldiers, Volume II: New York, Maryland, West Virginia and Ohio. Madison, WI: Federal Pub. Co., 1908.

Twenty-first Cavalry.—Cols., William B. Tibbits, Charles Fitz Simmons; Lieut. -Col., Charles Fitz Simmons; Majs., Charles G. Otis, George V. Boutelle, John S. Jennings. The 21st, known as the Griswold Light Cavalry, was recruited in the summer of 1863, in the counties of Rensselaer, Albany, Tioga and Monroe. The companies rendezvoused at Troy, where they were mustered into the U. S. service from Aug. 28, 1863, to Jan., 1864. A large portion of this regiment was mustered out by detachments and the remainder was consolidated on Sept. 9, 1865, into a battalion of seven companies, which was mustered out by detachments at Denver, Col., and Fort Leavenworth, Kan., from June 23 to Aug. 31. 1866. Five companies left the state on Sept. 4, 1863; one on Sept. 19; three on Oct. 19; one in November, and the others in Feb., 1864. The advance of the regiment served in the Department of Washington until Jan., 1864, when it was assigned to the ist brigade, ist cavalry division. Army of West Virginia. It was at Remount camp, Md., from Aug. to the close of Oct., 1864, then joined the Army of the Shenandoah and was assigned to the ist brigade, 2nd cavalry division. Its last active service was in the Department of West Virginia, from March, 1865. Throughout the year 1864, it was constantly employed in the arduous duties devolving on the cavalry arm of the service. Its greatest casualties were sustained at Lynchburg, loss 13; Buckton, loss 18; Purcellville, loss 21; Snicker's gap, loss 'iT, Ashby's gap, loss 28; Winchester, loss 21; Cedarville, loss 10; White Post, Va., loss 25. In 1865 it took part in engagements near Paris, Loudoun county, Va., White Post and near Berryville, where it was in action for the last time. Altogether it lost 3 officers and 63 men killed and died of wounds; 1 officer and 78 men died of disease, accidents, in prison, etc.; total deaths, 145. Capt. William H. Mitchell was killed in action at New Market, Va.; 1st Lieut. Nelson B. Holcomb died of wounds received in action at White Post, and 2nd Lieut. Charles H. Cone was killed in action at Ashby's gap.