Part of the War Department since 1789, Congress created the separate Ordnance Department, supervised by the Secretary of War, on 14 May 1812, as part of the War of 1812 preparations with responsibility for arms and ammunition production, acquisition, distribution and storage. The act also created a new position, the Commissary General of Ordnance.

On 5 February 1815 Colonel Decius Wadsworth, the former Commissary General of Purchases was chosen as the Commissary General of Ordnance. The act also directed the new Commissary General of Ordnance to "enlist artisans and laborers to direct the inspection and proof of all cannon and small arms to direct the construction of gun carriages equipments implements and ammunition to make estimates and contracts for and purchases of ordnance supplies and stores and to issue them to the army to exact from armories and arsenals quarterly returns of property and to receive from all responsible officers reports of damages to ordnance materiel to establish ordnance depots to prepare regulations for the government of the Ordnance Department and forms of returns and reports". In order to improve and reform the military's organization following the end of the War of 1812 the Army Reorganization Act of 3 March 1815 was passed, that among many other important changes[10] modified the responsibilities of the Ordnance Department "to include the procurement of arms and ammunition, supervision of the Army's arsenals and armories, and recruitment and training of artificers"[7] with the responsibility to arm and equip the militia from the permanent appropriation of $200,000 per annum provided by the law of 23 April 1808.

In 1821, all officers assigned to the Ordnance Department were re-commissioned into the artillery branch. The Ordnance Department would continue to function with officers from artillery. In 1832 an act of Congress would re-establish the Ordnance Department. On 3 August 1861, an Act of Congress added to the Ordnance Department the actual title of Chief of Ordnance "with the rank pay and emoluments of the Quartermaster General". On 1 January 1861, Brigadier General James Wolfe Ripley was promoted over the current Commissary General of Ordnance Colonel Henry K. Craig to become the first formally recognized Chief of Ordnance.

During the American Civil War, the Ordnance Department procured and provided massive amounts of weapons and supplies, and with the establishment of Sandy Hook Proving Ground, New Jersey, in 1874 the Army acquired its first full-scale testing facility. The Spanish–American War was the first conflict in which the department deployed materiel overseas and provided close combat support.