The Big Rodmans: 20-inch Rodmans, Part 2

In yesterday’s post on the 20-inch Rodman Gun, I’d mentioned the gun pictured below arrived at Fort Hamilton, New York for testing in the fall of 1864.

20-inch Rodman #1

Compared to the trials of the 15-inch gun, the 20-inch gun received a bit more fanfare – and full coverage in Harper’s Weekly. When first fired on October 26, 1864, those in attendance included the gun’s inventor Major Thomas J. Rodman; Army Chief of Ordnance, Brigadier General Alexander B. Dyer; Captain Henry Augustus Wise, Chief of the Navy’s Bureau of Ordnance; and General W. F. Smith. If illustrations accompanying the Harper’s article are any indication, a rather large crowd of onlookers joined the dignitaries.

“Large” was the word for every aspect of the gun. The gun rested upon a specially built 18 ton carriage from the Watertown Arsenal, which was also designed by Rodman. As a measure of the size of the gun, prior to firing, a man lowered himself into the bore of the gun and wormed down to the vent in order to clear an obstruction. 1

The objective of the test was only to verify the gun could fire the heavy projectiles. Unfortunately I’ve never come across any first hand account or report of the gun’s trials. Most secondary sources point to a caption in Francis Miller’s Photographic History of the Civil War. Although Miller incorrectly identified the photo of the 15-inch prototype as the 20-inch gun, he stated the big gun fired four shots in 1864. Firing a 1,080 pound solid shot, the gun used charges increasing through 50, 75, 100, and finally 125 pounds of powder. According to Miller, tests resumed in March 1867 with four more shots. This time charges of 125, 150, 175, and then 200 pounds, fired at a 25° elevation, propelled shot to a maximum range of 8,000 yards.2

Certainly impressive figures, but with the war winding down that massive iron gun was too much for peacetime budgets. Fort Pitt delivered one more 20-inch gun in 1869. This gun also survives today, on display at Fort Hancock, New Jersey. (And again let me thank Bill Coughlin for the photo.)

20-inch Rodman #2 at Fort Hancock

This gun bears the registry number 2 along with its weight marks of 115,100 pounds. John Alexander Kress inspected this monster gun. Once accepted, #2 went to Fort Monroe. In 1876 the gun went to Philadelphia for the Centennial Exposition.3

20-inch Rodman at Centennial Exposition

From there the gun eventually ended up at Fort Hancock among other heavy guns also undergoing trials in the later decades of the 19th century. Thankfully it was preserved to “guard” the post instead of being discarded.

Although the Army received only two 20-inch Rodmans, the guns significantly influenced post-war planning. Plans considered these largest of guns for the critical locations along the seacoast. Over the years, schemes for the 20-inch guns included more advanced carriages, muzzle loading rifled variants, and even breechloading conversions. None of these progressed far. Army acquisition at the time focused on refinement of weapons which could be mass produced in the event of war (since everyone felt there’d be ample warning before any future war). As such, the 1864 testimony of William Wade, part owner of the Fort Pitt Foundry, is worth note. When asked by the Joint Committee on the Conduct of the War, Wade indicated his foundry’s capacity was, “two 10-inch or 8-inch guns per day, three 15-inch guns per week, and two 20-inch guns per month.4

Perhaps we could end the story there, simply saying the two 20-inch Rodmans were great guns that were never called to action. But that’s not the case. In the late 1870’s Peru came shopping for weapons due to heated tensions with Bolivia and Chile. In addition to some of the 15-inch Rodmans, the Peruvians acquired at least on 20-inch Rodman (sometimes noted as a 1000-pdr gun), presumably a surplus weapon at the foundry. During the War of the Pacific, this Rodman, paired with a 20-inch Dahlgren gun also cast by Fort Pitt, was used in defense of the port of Callao. 5 The guns presumably wound up in the hands of the Chileans at that point. Perhaps the big Rodman guns did fire more than a few “test shots” after all.

The legacy of the 20-inch Rodman was to American seacoast defenses in the last decades of the 19th century. While the days of muzzleloading, black powder, smoothbores waned after the Civil War, the range of the 20-inch guns influenced plans. With these larger guns, defenders could control larger expanses of waterways. Instead of just defending the harbor entrances, the Coast Artillery could think about covering likely approaches to the coast. The real change would wait until modern breechloading, rifled, steel guns arrived.

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  1. Harper’s Weekly, Volume VIII, No. 412, November 19, 1864, page 749.
  2. Miller, Francis Trevelyan, The Photographic History of the Civil War: Volume 5 – Forts and Artillery (New York: Review of Reviews, 1911), page 137.
  3. Ingram, J.S., The Centennial Exposition Described and Illustrated (Philadelphia: Hubbard Brothers, 1876), page 146.
  4. Testimony of William Wade, “Heavy Ordnance,” Report of the Joint Committee on the Conduct of the War at the Second Session, Thirty-Eighth Congress (Washington: Government Printing Office, 1865), page 86.
  5. Markham, Sir Clements R., The War Between Peru and Chile, 1879-1882 (London: Sampson Low, Marston, and Company, 1882) page 186.