Recruited in late 1862, it fought from the Battle of Chancellorsville through the war until the Army of Northern Virginia's surrender at Appomattox Court House.

[2] The regiment was recruited in Beaver, Greene, Mercer, and Washington counties, and formally mustered into service on September 8, 1862, at Camp Curtin, under the command of Col. Richard P.

[3] The 140th was initially placed on duty guarding the North Central Railway near Parkton, Maryland, and remained there until being ordered to join the Army of the Potomac at Aquia Creek, Virginia, where they arrived on December 12.

Here they were assigned to the 3rd Brigade, 1st Division, II Army Corps, under the command of Gen. Samuel K. Zook, and proceeded to go into winter quarters near Falmouth, Virginia.

These were gratefully received by the men, as they had been subjected to continuous mockery by other soldiers with quips such as, “There goes the walking artillery” or, “Look at the twelve-pounders!”[3] On April 28, the 140th broke camp and marched with the II Corps around Gen. Robert E. Lee’s left flank, crossing the Rappahannock River at United States Ford and proceeding toward Chancellorsville, where it arrived on May 1 and took its place in the left center of Gen. Joseph Hooker’s line.

[4] Receiving orders on the evening of May 2 to report to Col. Nelson Miles, in charge of the 1st Division’s picket line, the men helped to beat back repeated Confederate assaults throughout the morning of May 3.

Thus Gen. Winfield Scott Hancock dispatched the 1st Division to report to Gen. George Sykes to be placed in line of battle to assist Sickles, moving to the latter's left end.

They initially made progress in pushing back the Rebels, but with the onset of Confederate reinforcements and the subsequent collapse of the III Corps to their right, as well as the withdrawal of the division on the left, the brigade was compelled to retreat.

Grant finding that Lee’s forces were too strongly entrenched there for a major assault, he ordered yet another eastward movement, this time in the direction of Cold Harbor.

During this period, the 140th was involved in various movements and smaller battles which comprised the overall siege, including Ream's Station on August 25, and Hatcher's Run February 5–7, 1865.