What Was the Largest Cannon Used in The Civil War?

What Was the Largest Cannon Used in The Civil War?

US Civil War
M1857 Napoleon at Stones River battlefield cemetery.
During the Civil War the Rodman guns were the largest in the U.S. arsenal.
Drawing comparing Model 1844 8-inch columbiad and Model 1861 10-inch “Rodman” columbiad. See the powder chamber on the older columbiad highlighted by the red box.
The 20-inch version would become the largest used during battle.
20-inch Rodman gun at the Centennial Exposition in Philadelphia, 1876. Hollow casting and the large guns produced using the method became considered showpieces of American technology.

However, the Rodman guns really didn’t see very much action at all during the war. They primary use was in coastal defense which really wasn’t a major pillar of Civil War combat.

8-inch Rodman converted rifles at Fort McHenry, Maryland. Mounted on post-war front pintle carriages.
Engraving showing a gun cast using Rodman’s hollow-casting technique. The engraving shows the gun mold in the casting pit. See the outer iron flask, the fire built outside the flask, and the cooling core also shown.
Period drawing of Rodman gun on a front-pintle barbette carriage
Period photograph of Battery Rodgers Alexandria, Virginia showing a 15-inch Rodman gun mounted on a center-pintle barbette carriage (rear) and an 8-inch (200-pounder) Parrott rifle mounted on a front-pintle barbette carriage (front). The 8-inch Parrott rifle used the same carriage as the 10-inch Rodman gun.
13-inch seacoast mortar, Model 1861, “The Dictator” on railroad cars during the siege of Petersburg.

Big cannons were really introduced into American warfare at sea. Before the USS Indiana battleship sailed with her 13 inch guns, the US Navy was installing big guns on their ships in the Civil War.

View on the forecastle, circa 1897, showing some of her crewmen, her pilothouse, forward 13-inch gun turret and forward port 8- inch gun turret. Halftone photograph, copied from the contemporary publication Uncle Sam’s Navy, 1898. U.S. Naval History and Heritage Command Photograph.
In fact, one of these big guns, named “The Dictator” was a 13 inch monster that put fear into the hearts of anyone who saw it.

The Federal 13-inch Seacoast Mortar, Model 1861 became designed to fire in a high arcing trajectory. Moreover, coming down on targets. As a result, this weapon could lob an almost 200-pound shell out to 4,300 yards. 

Moreover, the gun was not very mobile (weighing over 17,000 pounds), and slow to load and fire. Mainly used in siege warfare, for firing over walls and plunging down inside fortifications. 

Fred Gallup of the 8th Connecticut regiment wrote in a letter:

“Day before yesterday, in an experiment. Three shells from a 13 inch mortar was turned into or towards the city from off of a platform car. The third shot broke the frame. They are now constructing a heavier one.” —1862-65: Frederick Gallup to his Family
During the later part of the first year of the Civil War, there was a new 1861 Mortar model design. During the manufacturing phase, only 8 of the new 10″ models became produced. 

Manufactured by the Cyrus & Alger Co., the guns weighed approximately 7,300 lbs. In addition, took a 12 lb charge. Furthermore, could shoot a 98 lb projectile to a range of up to 2.5 miles, when fired at a 45 degree angle of elevation.

On one occasion, after firing five rounds on July 11th, the recoil of the mortar broke the flatcar it was sitting on, despite the flatcar’s reinforcement with iron rods and plates.

The Dictator at Petersburg on its rolling platform

As a result, the car needed repair and reinforcements before the gun returned to action. In addition, during the Battle of the Crater on 30 July 1864, the Dictator fired 19 rounds in support of the Union attack.

Painting of Fort Sumter showing exterior before the bombardment
Photograph showing Fort Sumter on August 23, 1863
Photograph of the 15-inch Rodman gun at Battery Rodgers, Alexandria, VA.
Another photograph of the 15-inch Rodman gun at Battery Rodgers. This photograph gives an excellent view of the elevation mechanism and the center-pintle carriage.
15-inch Rodman gun at Battery Rodgers, Alexandria, Virginia, mounted to defend the Potomac River as part of the Defenses of Washington.
The 15-inch Rodman Gun (better known as the Floyd Gun) in 1860 at the Fort Pitt Foundry, Pittsburg, Pa.

On November 14, 1864, and February 20, 1865, Confederate General Joseph Anderson would cast two 12-inch cannons at the south’s largest ironworks in Richmond, Tredegar Iron Works.

Cropped detail of a photograph of the Tredegar Iron Works in Richmond, Va., taken after the fall of Richmond in April 1865, focusing on the iron work structures.

However, for General Anderson these cannons would become finished far too late for any real usefulness in the war. And as a result, unluckily for the Confederacy the guns never became finished. Unfortunately for the south, they lacked the raw materials and technical know-how that Northern industry possessed. One Southern officer wrote of the situation:

Joseph Reid Anderson, a General of the Confederate States Army during the American Civil War (shown in uniform). The proprietor of the Tredegar Iron Works in Richmond, Virginia. After he was injured in battle, he spent the remainder of the war working in the Ordinance Department. Library of Congress, Prints and Photographs Division Washington, D.C. Original photograph ca. 1861-1865; Confederate States of America military photo; Forms part of Civil War glass negative collection

“The combination of Yankee artillery with Rebel infantry would make an army that could be beaten by no one.”

What Was the Largest Cannon Used in The Civil War?

US Civil War

Eric Foner on the Civil War. Pulitzer Prize Winning in addition Columbia History Professor