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

This regiment was raised by Col. John Cochrane, under authority from the War Department, dated June 11, 1861; organized at Camp Tompkins, Willett's Point, L. 1., and there mustered in the service of the United States for three years in July and August, 1861. At the expiration of its term of service, the regiment was retained in service, but, September 1, 1864, consolidated into a battalion of four companies, C, F, G and H; the men entitled thereto were honorably discharged September 12, 1864, in New York City. September 1, 1864, the members of the 67th Infantry, not mustered out with their regiment, were transferred to this as Companies A, B, D and E. In March, 1865, Companies I and K were reformed of recruits. June 24, 1865, the men of the 12lst Infantry not discharged with their regiment, were transferred to this.
The companies were recruited principally: A, C, G and I in New York City; B in Maine, Rhode Island and the Hudson river counties; D in New York city and Troy; E in New York City, Connecticut and Rhode Island; F and H in New York City and Rhode Island, and K in New York City and Ohio.
The regiment left the State August 27, 1861; served in the 3d Provisional, Baker's, Brigade, from September, 1861; in Graham's Brigade, Buell's,. later Keyes', Division, Army of the Potomac, from September 19, 1861; in Graham's, 2d, Brigade, Couch's, 1st, Division, 4th Corps, Army of the Potomac, from March 13, 1862; in 3d Brigade, 1st Division, 4th Corps, Army of the Potomac, from September, 1862; in 3d Brigade, 3d Division, 6th Corps, Army of the Potomac, from September 26, 1862; in 1st Brigade, 3d Division, 6th Corps, Army of the Potomac, from December, 1862; on Johnson's Island, Lake Erie, Ohio, from January, 1864; in 4th Brigade, 1st Division, 6th Corps, Army of the Potomac, from March, 1864; in 2d Brigade, 1st Division, 6th Corps, from July 6, 1864; and it was honorably discharged and mustered out, commanded by Col. Henry C. Fisk, July 17, 1865, at Halls Hill, Va.
During its service the regiment lost by death, killed in action, 4 officers, 80 enlisted men; of wounds received in action, 1 officer, 36 enlisted men; of disease and other causes, 2 officers, 88 enlisted men; total, 7 officers, 204 enlisted men; aggregate, 211; of whom 25 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. Madison, WI: Federal Pub. Co., 1908. volume II. 

Sixty-fifth Infantry.—Cols., John Cochrane, Alexander Shaler, Joseph E. Hamblin, Henry C. Fiske; Lieut.-Cols., Alexander Sha-ler, Joseph E. Hamblin, Henry J. Healy, Thomas H. Higginboth-am, Henry C. Fiske, David I. Miln; Majs., Henry J. Healey, Thomas H. Higginbotham, David I. Miln, Edmund K. Russell. The 65th, known as the U. S. Chausseurs, composed of members from Eastern New York and a number from Connecticut, Rhode Island and Maine, was mustered into the U. S. service at Willett's Point, L. I., in July and Aug., 1861, for three years. It left the state for Washington on Aug. 27, was assigned to the 3d provisional brigade until Sept. 19, when it became a part of Graham's brigade, Buell's division, and in March, 1862, joined the advance to the Peninsula as a part of the 2nd brigade, 1st division, 4th corps. It was present at the siege of Yorktown and active during the Seven Days' battles, with a loss of 68 in killed, wounded and missing. At Antietam it was again engaged, but did not occupy an exposed position, and during the month of Sept., 1862, the division was transferred to the 6th corps, in which it became the 3d division. The 65th served in the 3d brigade until December and was then assigned to the 1st brigade. At Fredericksburg the regiment was present, but not closely engaged, and the winter was passed in that vicinity. In the Chancellorsville campaign the 65th shared in the charge which captured Marye's heights. After returning for a brief period to its old camp it proceeded to Gettysburg, where it was held in support, then moved southward with the army, shared in the Mine Run campaign and went into winter quarters with the 6th corps. In Jan., 1864, the regiment was sent to Johnson's island in charge of prisoners, and upon its return to the Army of the Potomac was attached to the 4th brigade of its old division. A sufficiently large number of the men reenlisted to secure the continuance in the field of the 65th as a veteran organization and it fought through the Wilderness campaign with brilliancy, losing during the first week 154 members killed, wounded or missing, many of whom fell in the assault on the angle at Spottsylvania. At Cold Harbor and Petersburg the regiment was active and when the 6th corps was sent to Washington to repel Gen. Early, the 65th was assigned to the 2nd brigade of the same division with which it had previously served. It embarked for Washington July 10, 1864, encountered Early at Fort Stevens and pursued him through the Shenandoah Valley, fighting at Charlestown, the Opequan, Fisher's hill, and Cedar creek. In the last named action the regiment took a prominent part and suffered the loss of 90 in killed, wounded and missing. It returned to Petersburg in December; was engaged at Hatcher's run in Feb., 1865, at Fort Stedman, and the final assault on April 2. In Sept., 1864, the original members not reenlisted were mustered out and the veterans and recruits consolidated into a battalion of four companies, which received the addition of four companies of the 67th N. Y., and in March, 1865, two companies of new recruits. The regiment was mustered out at Washington, July 17, 1865, having lost during its term of service 121 by death from wounds and 90 from other causes.