The 16th Pennsylvania Cavalry was organized at Harrisburg, Pennsylvania beginning in September 1862 as the "161st Volunteers" and mustered in for three years service under the command of Colonel John Irvin Gregg.

Averill's Cavalry Brigade, Army of the Potomac, to February 1863.

2nd Brigade, 2nd Division, Cavalry Corps, Army of the Potomac, to June 1863.

3rd Brigade, 2nd Division, Cavalry Corps, Army of the Potomac, to August 1863.

2nd Brigade, 2nd Division, Cavalry Corps, Army of the Potomac, to May 1865.

It was then stationed at Camp Casey, near Bladensburg, Maryland, until January 3, 1863.

The regiment then took up duty on the line of the Rappahannock River until April 1863.

It was involved in operations at Rappahannock Bridge and Grove Church February 5–7.

Brandy Station, Stevensburg, and Beverly Ford June 9.

Amissville, Gaines Cross Roads, and Sperryville December 22.

The regiment started 1864 off by participating in Kilpatrick's Raid on Richmond February 28-March 4, 1864.

Black Creek or Tunstall Station June 21.

Siege operations against Petersburg and Richmond July 1864 to April 1865.

Demonstration on north side of the James at Deep Bottom July 27–29.

Demonstration on north side of James River at Deep Bottom August 13–20.

Strawberry Plains, Deep Bottom, August 14–18.

Boydton Plank Road, Hatcher's Run, October 27–28.

Paine's Cross Roads and Amelia Springs April 5.

Moved to Lynchburg, Va., and duty there and in the Department of Virginia until August.