The 142nd New York Infantry was organized at Ogdensburg, New York, beginning August 14, 1862 and mustered in for three-years service on September 29, 1862 under the command of Colonel Roscius W. Judson.

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.

1st Brigade, 1st Division, XI Corps, Army of the Potomac, to August 1863.

1st Brigade, Gordon's Division, Northern District, Department of the South, to April 1864.

1st Brigade, 2nd Division, X Corps, Army of the James, Department of Virginia and North Carolina, to May 1864.

1st Brigade, 2nd Division, Terry's Provisional Corps, Department of North Carolina, to March 1865.

1st Brigade, 2nd Division, X Corps, Army of the Ohio, Department of North Carolina, to June 1865.

Butler's Campaign on the south side of the James River and operations against Petersburg and Richmond May 4–28.

Siege operations against Petersburg and Richmond June 16, 1864 to December 7, 1864.

Duty in trenches before Petersburg and on the Bermuda Hundred front until September 27.

Battle of Chaffin's Farm, New Market Heights, September 28–30.