During the Mexican-American War the U.S. found itself lacking in light guns that could be fired from ships’ boats and landed to be used as light artillery in support of landing parties . Light artillery borrowed from the army proved unsatisfactory. In 1849, then Lieutenant, Dahlgren began to design a family of smooth bore muzzle loading boat howitzers that could be mounted in ships’ launches and cutters as well as being mounted onto field carriages. The first boat howitzers to be designed were a light 12-pounder, a heavy 12-pounder (originally designated a “medium”), and a 24-pounder. Later a lighter 12-pounder (the “small”) and a rifled 12-pounder heavy howitzer were introduced. All of the boat howitzers were very similar in design, cast in bronze, with a mounting lug or loop on the bottom of the barrel instead of trunnions, and an elevating screw running through the cascabel. Having the single mounting lug expedited moving the howitzer form the launch to field carriage and back. In naval service the boat howitzers had gun crews of 10 in the boat and 11 ashore. The field carriage was made of wrought iron. No limber was used in naval service, but two ammunition boxes (each containing nine rounds) could be lashed to the axle of the field carriage. Members of the gun crew also carried a single round in an ammunition pouch. The smoothbore boat howitzers fired shell, shrapnel, and canister. The rifled 12-pounder fired shot and shell. Percussion primers were used in naval service, but the howitzers could also use friction primers obtained from the army.
The small and the light 12-pounder boat howitzers were not popular. The heavy 12-pounder howitzers were most popular at their intended jobs, while the 23-pounder boat howitzer were found to serve excellently as primary and secondary armaments on river gunboats and similar small vessels. Some 24-pounder boat howitzers were apparently rifled, but some contemporary accounts confuse rifled 24-pounder boat howitzers and the 20-pounder rifles (discussed below)
Aside from use in naval service, boat howitzers saw service with the land forces as well. The boat howitzers were occasionally used in artillery batteries, but were more often used in infantry units, in a role that would later be called infantry support guns.
At First Bull Run, two boat howitzers were manned by Company I of the 71st Regiment, NY National Guard. The unit had trained on boat howitzers while deployed at Washington D.C., and when called to Bull Run, brought two of them attached to I Company. The guns unfortunately had to be left behind during the unit's withdraw and were captured by Confederate forces.
During the Antietam campaign, the 9th NY Infantry (Hawkins' Zouaves), Company K (Whiting's Battery) employed 5 Dahlgren Boat Howitzers (two rifled and two smoothbores) They fired on Confederate skirmishers at Snavely's Ford and suppressed them . The Confederate Grimes' (Portsmouth) Battery had 2 smoothbore Dahlgren Boat Howitzers, with which they fought near Piper's Stone Barn . The boat howitzers appeared to be popular - when Grime's battery was forced to turn in one of its guns, it chose to turn in a 3-inch Ordnance Rifle rather than one of its Boat Howitzers .
The 1st Regiment, New York Marine Artillery also armed themselves with boat howitzers, using it for its designed use of amphibious expeditions. The unit participated in 16 raids along the North Carolina coast employing their boat howitzers. The New York Marine Artillery was issued twelve 12-pounder rifled boat howitzers made by Norman Wiard out of semi-steel, a low-carbon iron alloy. Other than the material used, the Wiard boat howitzers were identical to the Dahlgren 12-pounder rifled boat howitzers. The Wiard howitzers were not made in large numbers .
Boat howitzers were used in the western theaters also. The Indiana Brigade used a Dahlgren boat howitzer in fighting near Grand Prairie, Arkansas on July 5, 1862. .
While boat howitzers were never commonly used by either army, by the end of the war their use by land forces was very rare.
|Designation||Bore||Length Overall||Weight||Service Charge||Range (yards)||Number Made|
|12-pdr small||4.62 in||32.5 in||300 lb||23|
|12-pdr light||4.62 in||51.75 in||430 lb||10 oz||177|
|12-pdr heavy||4.62 in||63.5 in||750 lb||1 lb.||1,085 at 5° elev.||456|
|12-pdr rifled||3.4 in||63.5 in||880 lb||1 lb||1,770 at 6° elev.||424|
|24-pdr||5.82 in||67 in||1,300 lb||2 lb||1,270 at 11° elev.||1,009|
32-pounder gun of 4500 pounds and VIII-inch Dahlgren Shell Gun - 383 of the 32-pounders and 355 of the VIII-inch Dahlgren were cast by Alger, Builders, Fort Pitt, and Seyfert, McManus & Co. between 1864 and 1867. The 32-pounder had a crew of 10 and a “powder-boy” while the VIII-inch had a crew of 12 and a “powder-boy.” Some have argued that these guns are not Dahlgren designs, pointing out that while the guns generally resemble his designs, these guns used an old-style breeching jaws instead of the breech loop found on other Dahlgrens and that there is no elevating screw running through the cascabel . It is also asserted that the guns would have to be elevated by quoins. This is not accurate, particularly for the VIII-inch Dahlgren, as a new iron carriage with an elevating screw beneath the breech of the gun was developed for VIII-inch and other carriages with breech elevating screws were also used . It is also argued that the bores were too small for their late introduction and very few saw service during or after the American Civil War. These guns would most likely have been intended for small riverine and estuarine gunboats, which the Navy scrapped as quickly as possible after the war. The documentary evidence also supports a conclusion that these two guns should be considered to be Dahlgen designs. In Mrs. Dahlgren’s petition to the national government for compensation for the use of Admiral Dahlgren's inventions, both the 32-pounder gun of 4500 pounds and VIII-inch shell gun are specifically described as designs of Admiral Dahlgren . Also in February 1867, Cyrus Alger paid a royalty on the Dahlgren patent for production of “ten 8-inch guns weighing 64,270, $642.70.” There can be little doubt that both of these guns should be credited as Dahlgren designs.
IX-inch Dahlgren shell gun - 1,185 guns were cast at Alger, Bellona, Fort Pitt, Seyfert, McManus & Co., Tredegar, and West Point foundries between 1855 and 1864. Fort Pitt Foundry also made 16 for the Army in 1861. The IX-inch Dahlgren was the most popular and versatile of Dahlgren Shell guns made. The IX- guns served as broadside armament on larger ships such as the USS Susquehanna, which carried 12 IX-inch Dahlgren guns in broadside mounts in addition to her two pivot guns and the USS Powhatan which carried 10 IX-inch guns in broadside mounts in addition to her 2 XI-inch Dahlgren pivot guns. These broadside guns would normally be mounted on a Marsilly carriage (see illustration). Smaller coastal blockade ships such as the USS Fort Henry and the USS Hunchback mounted IX-inch Dahlgrens on pivot mounts. IX-inch Dahlgrens were used on several river gunboats such as the USS Essex and the USS. Benton. If mounted as either a pivot gun or a broadside gun the IX-inch Dahlgren had a crew of 16 and a “powderman.”
X-inch Dahlgren shell gun (light) - 10 were cast at Seyfert, McManus & Co. and West Point Foundries between 1855 and 1864. Pivot mounted on board ships such as U.S.S. Brooklyn and USS Merrimack (pre-CSS Virginia) with a crew of 20 and a “powderman.”
X-inch Dahlgren shell gun (heavy) - 34 cast between 1862 and 1865. Designed from the beginning to fire shot against armored ships with heavier powder charges. Mounted on a pivot mount with a crew of 20 and a “powderman."
XI-inch Dahlgren shell gun - 465 were cast at Alger; Builders; Fort Pitt; Hinkley, Williams & Co.; Portland Locomotive Works; Seyfert, McManus & Co.; Trenton Iron Works; and West Point foundries between 1856 and 1864. This is the only Dahlgren gun to have been designed both with and without a muzzle swell. The gun was typically mounted on a pivot or in a turret on a monitor. When mounted in a turret, the crew for an XI-inch Dahlgren was 7 including powdermen. The crew for the gun when mounted on a pivot was 24 men and a “powderman.” XI-inch Dahlgrens were carried on Neosho, Marietta, Casco, Milwaukee, and (1 XI-inch and 1 XV-inch short) class monitors as well as the original USS Monitor. The USS Kearsarge, USS Powhatan, and many other conventional ships carried XI-inch Dahlgrens on pivot mounts. A few larger river gunboats, such as the USS Tuscumbia and USS Indianola also carried XI-inch Dahlgrens.
XIII-inch Dahlgren shell gun - The XIII-inch Dahlgren was originally intended for the Passaic class monitors but proved unsuccessful and the XV-inch Dahlgren was used instead.
XV-inch Dahlgren shell gun (short or “Passaic”) - 34 were cast by the Fort Pitt Foundry between 1862 and 1864 . The first XV-inch guns' barrels were so short that the muzzle was inside the monitor's turret when the gun was discharged. The resulting blast and fumes in the turret would have made the gun impossible to work. The Navy constructed “smoke-boxes” inside the turrets of the monitors equipped with the short XV-inch gun (see illustration), but the presence of the smoke-boxes slowed the rate of fire for the guns. When mounted in a turret, the crew for a XV-inch Dahlgren was 10 including powdermen. Carried on Passaic (1 XI-inch and 1 XV-inch short) and early Canonicus class monitors.
XV-inch Dahlgren shell gun (long or “Tecumseh”) - 86 were cast by the Alger, Fort Pitt, and Seyfert, McManus & Co. foundries between 1864 and 1872 . The new XV-inch gun was lengthened 16 inches so that the muzzle was flush with the outside of the turret when fired, eliminating the need for the smoke-box, Carried on later Canonicus class monitors. XX-inch Dahlgren shell gun - 4 were cast by the Fort Pitt Foundry between 1864 and 1867. Three were accepted by the U.S. Navy, but saw no service. The fourth gun was sold to Peru.
|Designation (bore)||Length Overall||Weight of Gun||Weight of Shot||Weight of Shell||Service Charge||Range (yards)|
|32-pdr. of 27 cwt. (6.2 inch)||93.72 in.||3,3200 lb.||32 lb.||26.5 lb.||4 lb.||1637 @ 6° elev.|
|32-pdr of 4,500 lb. M.1864 (6.2 inch)||107.5 in.||4,500 lb.||32 lb.||26.5 lb.||6 lb.||1756 @ 5° elev.|
|VIII-inch||115.5 in.||6,500 lb.||65 lb.||52.7 lb.||7lb.||2600 @ 11° elev.|
|IX-inch||131 in.||9,000 lb.||90 lb.||73.5 lb.||13 lb.||3450 @ 15° elev.|
|X-inch||146 in.*||12,000 lb.||124 lb.||101.5 lb.||12.5 lb.||3000 @ 11° elev.|
|X-inch (heavy)||145 in.*||16,500 lb.||124 lb.||101.5 lb.||18 lb.||----|
|XI-inch||161 in.||15,700 lb.||166 lb.||133.5 lb.||20 lb.||3650 @ 15° elev.|
|XIII-inch||162 in.*||36,00 lb.||276 lb.||216.5 lb.||40 lb.||----|
|XV-inch Short "Passaic"||162 in.*||42,000 lb.||440 lb.||352 lb.||35 lb.||2100 @ 7° elev.|
|XV-inch Long "Tecumseh"||178 in.*||43,000 lb.||440 lb.||352 lb.||35 lb.||2100 @ 7° elev.|
|XX-inch||204 in.||100,000 lb.||1,080 lb.*||100 lbs.||----|
Estimated values are indicated by an asterisk. Estimates by , except for the estimate of the overall length of the X-inch (heavy) which is based on a bore length of 117.75 inches and the estimate of the weight of the XX-inch shell which is based on the weight of the shell for the Columbiad, Seacoast, 20-inch, Model 1864.
20-pounder rifle - An entirely bronze gun that was popular and was the only Dahlgren rifle (other than the 12-pounder boat howitzer) that continued in service after the American Civil War. Crew of 6 and a “powder-boy” firing a 20 lb. shell in front of 2 lb. of powder it had a range of 1,960 yards at a 6.5º elevation.
30-pounder rifle - These guns were iron with bronze trunnions and trunnion bands. They were cast at the Fort Pitt foundry and the Washington Navy Yard. In February 1862, Dahlgren recommended that the first 13 cast at Fort Pitt be withdrawn because the iron was inferior. One 30-pounder rifle was mounted on the USS Harriet Lane.
50-pounder rifle - These guns were typical Dahlgren rifles--iron with bronze trunnions and trunnion bands. They were apparently a popular design, although by the end of the war it had been supplanted by the 60-pounder Parrott rifle, which coninued in service after the American Civil War. A photograph of Admiral Dahlgren leaning against a 50-pounder rifle may be found at the beginning of this article. 80-pounder rifle - The first 80-pounder was cast at the West Point foundry with trunnions. Subsequent rifles were cast without trunnions and bronze trunnion band and trunnions were added. The gun was initially well received but soon showed a tendency to burst. The USS Hetzel, a converted Coastal Survey ship armed with 1 IX-inch Dahlgren and 1 80-pounder Dahlgren rifle was engaged in the bombardment of Roanoke Island in support amphibious landings, when the following entry was made in her log for February 7, 1862: “At 5:15, rifled 80-pounder aft, loaded with 6 pounds powder and solid Dahlgren shot, 80 pounds, burst in the act of firing into four principal pieces. The gun forward of the trunnions fell on deck. One third of the breech passed over the mastheads and fell clear of the ship on the starboard bow. One struck on port quarter. And the fourth piece, weighing about 1,000 pounds, driving through the deck and magazine, bringing up on the keelson, set fire to the ship. Fire promptly extinguished.”
150-pounder rifle - The 150-pounder was a typical Dahlgren rifle with an cast iron barrel and a bronze trunnion band and trunnions. Although the test firing was successful the guns were not placed in service, because Dahlgren doubted the quality of the iron.
12-inch rifle - In 1864 the Fort Pitt foundry bored 3 XV-inch Dahlgren shell gun blanks, one was finished using the Atwater design, one with the Parrott design, and one with the Rodman approach. The Rodman solid shot weighed 618 to 619 pounds and the Atwater solid shot 416 to 535 pounds. The weights of the Parrott projectiles are not recorded. In 1867, at Fort Monroe, the guns were tested with charges varying between 35 and 55 pound until the guns failed.
|Designation||Bore||Length Overall||Weight of Gun||Service Charge||Number Made|
|20-pdr rifle||4 in.||1,340 lb.||2 lb.||100|
|30-pdr rifle||4.2 inc.||92 in.||3,200 pounds||55|
|50-pdr rifle||5.1 in.||107 in.||3,596 lb.||34|
|80-pdr rifle||6 in.||6 lb.||14|
|150-pdr rifle||7.5 in.||140 in.*||5|
|12 in. rifle||12 in.||178 in.*||45,500 lb.||35-55 lb.||3|
Estimated values are indicated by an asterisk. Estimates by .
Chairman of Maritime History, Kyle Rapp Ph.D, M.D