John Adolph Bernard Dahlgren, (1809–1870)


John Dahlgren next to one of his 4.4-inch or 5.1-inch rifled guns on the USS Pawnee. (Library of Congress)


The crew of a Dahlgren gun at drill aboard the U.S. gunboat Mendota, 1864. (National Archives)

U.S. admiral and developer of an ordnance system named for him. Born in Philadelphia on 13 November 1809, John Dahlgren was the son of the Swedish consul. His father’s death in 1824 led Dahlgren to apply to become a midshipman. Turned down, Dahlgren shipped out as a merchant seaman. In February 1826 he secured appointment as an acting midshipman and then served on the USS Macedonian and Ontario.

Assigned to the Coast Survey during 1834–1837, Dahlgren demonstrated an aptitude for math and science; he made lieutenant in March 1837. But this assignment caused serious eye problems and led to two years ashore, detached from service. After his return to active duty, during 1843–1844 he served on the Cumberland in the Mediterranean, where he befriended Lieutenant Andrew H. Foote.

In 1844 Dahlgren was assigned to direct ordnance activities at the Washington Navy Yard. Here he found his calling. Dahlgren designed new firing mechanisms and new sights. In 1848 he tested 32-pounders and 8-inch guns and for the first time produced ranging data on these guns. In 1849 Dahlgren developed a new system of boat howitzers, but he is chiefly remembered for his system of heavy smoothbore muzzle-loading ordnance. He also designed rifled guns, but they were not successful, and in 1862 most were withdrawn from service.

Dahlgren made commander in September 1855, and when commandant of the Washington Navy Yard Captain Franklin Buchanan joined the Confederacy early in 1861, Dahlgren replaced him. He was promoted to captain in July 1862 and then to rear admiral in February 1863.

Dahlgren very much wanted a command at sea. Never popular with his brother officers because of his relentless pursuit of recognition and his self-promotion, he used his influence with President Abraham Lincoln to advantage. When Secretary of the Navy Gideon Welles replaced Admiral Samuel Du Pont as commander of the South Atlantic Blockading Squadron, and after Welles’s choice, Admiral Andrew Foote, died suddenly, Dahlgren got that command.

Most of Dahlgren’s time in his new command was spent off Charleston trying to seal that harbor and protect his squadron. He personally led attacks by monitors on the Confederate forts but, like Du Pont before him, was unable to take Charleston. Also as with Du Pont, he was unwilling to run risks and rejected an attempt to force the inner harbor. A boat attack on Fort Sumter, on the night of 8 September 1863, failed. He did assist Union land forces in taking Savannah and ultimately Charleston, and he directed an expedition up the St. John’s River in Florida.

After the war Dahlgren commanded the South Pacific Squadron for two years. He then returned to head the Bureau of Ordnance. During his naval career Dahlgren was a prolific author on ordnance subjects. At the time of his death on 12 July 1870, he commanded the Washington Navy Yard.

Dahlgren Guns

Name given to a system of guns developed by U.S. Navy Commander John A. Dahlgren and used extensively by both sides during the U.S. Civil War. Dahlgren, assigned to the Washington Navy Yard in 1844, soon was developing ordnance innovations and a new system of ordnance.

In 1849 Dahlgren produced a new howitzer. Cast of bronze, these appeared as 12-pounders (light, 660 lb., and heavy, 750 lb.) and 24-pounder smoothbores (1,300 lb.). There were also 3.4-inch (12-pounder, 870 lb.) and 4-inch (20-pounder, 1,350 lb.) rifles. The finest boat guns of their day in the world, they remained in service with the U.S. Navy until the 1880s and were also copied by other navies.

Dahlgren is known chiefly for his system of heavy smoothbore, muzzle-loading ordnance. The first prototype IX-inch gun (shell guns were designated in the U.S. Navy with a Roman numeral) was cast in May 1850. Dahlgren guns, with their smooth exterior, curved lines, and weight of metal at the breech, looked like soda water bottles and were sometimes so called. Dahlgren designed them to place the greatest weight of metal at the point of greatest strain at the breech. The IX-inch was the most common broadside, carriage-mounted gun in the U.S. Navy during the Civil War; the XI-inch, the prototype of which was cast in 1851, was the most widely used pivot-mounted gun. The XI-inch shell could pierce 4.5 inches of plate iron backed by 20 inches of solid oak.

Dahlgren guns appeared in a variety of sizes: 32-pounder (3,300 and 4,500 lb.), VIII-inch (6,500 lb.), IX-inch (12,280 lb.), X-inch (12,500 lb. for shell and 16,500 lb. for shot), XI-inch (16,000 lb.), XIII-inch (34,000 lb.), and XV-inch (42,000 lb.). There was even a gun of XX-inch bore (97,300 lb.), which, however, did not see service aboard ship during the war. XV-inchers were used aboard Union monitors.

Dahlgren guns also appeared as rifles, somewhat similar in shape to the smoothbores. Some of these had separate bronze trunnion and breech straps. Dahlgren rifles appeared as 4.4-inch/30-pounder (3,200 lb.), 5.1-inch/50-pounder (5,100 lb.), 6-inch/80-pounder (8,000 lb.), 7.5-inch/150-pounder (16,700 lb.), and 12-inch (45,520 lb., only three of which were cast). The Dahlgren rifles were not as successful as his smoothbores, and in February 1862 most were withdrawn from service.

With the exception of the rifles, Dahlgren guns were extraordinarily reliable. It is ironic that having been developed to project shell against wooden ships, the guns were often used during the Civil War to fire solid shot against Confederate ironclads.


Dahlgren, John A. Shells and Shell Guns. Philadelphia: King &Baird, 1856.

Dahlgren, Madeleine Vinton. Memoir of John A. Dahlgren, Rear-Admiral United States Navy. Boston: James R. Osgood, 1882.

Olmstead, Edwin, Wayne Stark, and Spencer Tucker. The Big Guns: Civil War Siege, Seacoast and Naval Cannon. Alexandria Bay, NY, and Bloomfield, Ontario, Canada: Museum Restoration Service, 1997.

Schneller, Robert J., Jr. A Quest for Glory: A Biography of Rear Admiral John A. Dahlgren. Annapolis, MD: Naval Institute Press, 1996.


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