These innovative artillery pieces were invented by Robert Parker Parrott in 1860. He was the superintendent the West Point Iron and Cannon Foundry in Cold Spring, New York. These 20-pounders were the largest field guns used in the Civil War and are rarer than the 10-pounders. The Confederates also produced copies of this design. The 20-pounders could fire 19 pound shells a maximum of 4,400 yards. It has "R.P.P." (Robert Parker Parrott) on the right trunnion, "20 PDR" on the left trunnion, "US" on top, "1700 No 221. 1864. W.P.F./D.W.F. 3.67" on the muzzle (1700 pound weight, number 221, manufactured at the West Point Foundy in 1864, and inspected by Daniel Webster Flagle), and an Paulson Bros. Ordnance Corp. carriage.