The 143rd New York Infantry was organized at Monticello, New York, beginning August 14, 1862 and mustered in for three years service on October 8, 1862 under the command of Colonel David P. DeWitt.

The regiment was attached to 3rd Brigade, Abercrombie's Division, Defenses of Washington, D.C., to February 1863.

3rd Brigade, Abercrombie's Division, XXII Corps, Department of Washington, to April 1863.

2nd Brigade, 3rd Division, VII Corps, Department of Virginia, to May 1863.

1st Brigade, 2nd Division, IV Corps, to July, 1863.

3rd Brigade, 1st Division, XX Corps, Army of the Cumberland, to July 1865.

October 28–29: Battle of Wauhatchie, Tenn. November 23–27: Chattanooga-Ringgold Campaign.

May 26—June 5: Battles about Dallas, New Hope Church, and Allatoona Hills.

July 4: Ruff's Station or Smyrna Camp Ground.

August 26—September 2: Operations at Chattahoochie River Bridge.

October 26–29: Expedition from Atlanta to Tuckum's Cross Roads.