Born on November 12, 1842, at Providence, Rhode Island, John Pitman enlisted at the outbreak of the Civil War in the 1st Rhode Island Infantry. He enlisted again in 1862 as a private in the 10th Rhode Island Infantry, advancing to the rank of Sergeant Major. In April 1893, he received a commission in the 11th Rhode Island Infantry, mustering out in July of that year to accept a Presidential appointment to the United States Military Academy.
Graduating in 1867, Pitman chose service in the Ordnance Department. Following assignments at St. Louis Arsenal, West Point, and Watervliet Arsenal; he served from 1876 to 1886 at the Watertown Arsenal in Massachusetts, where he was responsible for the Emery Testing Machine, the latest device for measuring the strength and properties of metals. He also established a laboratory at the arsenal and gained additional experience in chemistry, mineralogy, and geology during three years of detached service with the Interior Department in the Division of Mining Geology of the United States Geological Survey.
Next, Pitman was appointed Chief Ordnance Officer of the Department of Dakota, where he was responsible for moving the department's Ordnance Depot from Fort D. A. Lincoln, North Dakota, to Fort Snelling, Minnesota. In 1890, he was detailed to the West Point Foundry, where he inspected the assembly of 8-inch breech-loading rifles. In 1892, the Chief of Ordnance directed Pitman to establish a laboratory at the Frankford Arsenal in Philadelphia to study and develop smokeless powders. Several European powers had developed such powder, and the US needed to catch up. Pitman set up the laboratory, devising his own equipment and test procedures. He developed a perforated, smokeless-propellant grain still in use today. He also expanded the laboratory's research into all types of explosives. The Ordnance Department recognized his work in 1948 by renaming the laboratory the Pitman-Dunn Laboratory; Captain B. W. Dunn was a fellow Ordnance officer who developed explosives at Frankford Arsenal in the 1890s.>
Pitman departed Frankford Arsenal in 1898 to serve as Commander of the Augusta Arsenal and Armament Officer of the Southern District. In 1902, he served as Deputy Commander of the Springfield Armory; and then in 1903, was assigned as Commander, San Antonio Arsenal, and Chief Ordnance Officer for the Department of Texas. In 1906, at the age of 64, he retired at the rank of Colonel and was promoted to Brigadier General, Retired, based on his Civil War service.
Pitman's contributions by no means ended with his retirement. Throughout his career and into retirement, he collected data on small arms and ammunition, including photographs, prints, memos, and letters from multiple sources. He amassed 16 volumes of data, 5 volumes of which were published as The Pitman Notes. He also collected experimental guns, specialty weapons, pistols, and foreign weapons, to include the ammunition. Pitman died on August 29, 1933, and is buried in Providence, Rhode Island. He donated much of his library and collection to the United States Military Academy. His cartridge collection alone fills over 100 drawers in three cabinets at the West Point Ordnance Museum. In 42 years of service and well into retirement, Brigadier General Pitman made invaluable contributions to the development of small arms, explosives, and propellants.