Neptune's Needle

Naval officer. In February 1826 Dahlgren was granted an appointment as a midshipman in the U.S. Navy. His first assignment was to the frigate Macedonian under Captain James Barron on the Brazil station. His second voyage was aboard the sloop Ontario (1829-1831) in the Mediterranean. After a period of shore duty in 1834, he was assigned to the Coast Survey. During his service with the Coast Survey (1834-1837), Dahlgren displayed considerable ability at mathematics. He was promoted to lieutenant 8 May 1837.

He left in November 1843 to sail aboard the Cumberland, bound for the Mediterranean station. He returned to Wilmington in November 1845, and was ordered in January 1847 to report to Washington for duty with the Ordnance Department of the navy. Dahlgren so impressed his superiors that in August he was given direction of all ordnance matters at the Washington Navy Yard.

During his years at the Washington Navy Yard Dahlgren improved production methods and also introduced in 1850 his design for a new type of large cannon capable of withstanding the pressure required to fire heavy shot. Each Dahlgren Gun was cast with a uniform diameter so that the metal would cool evenly. The barrel was then machined to produce a thin muzzle and a thick breech, the latter being necessary to withstand the intense pressure produced by exploding powder. This method allowed the manufacture of large-caliber guns that were still light enough to be useful aboard ships. The shape of the guns was similar to that of the bottles in which soda was purchased, and so they were often called "soda-water guns." Dahlgren Guns became immensely popular and played a critical role in arming navies in the United States and elsewhere.

Dahlgren was also responsible for the invention of a small, lightweight brass howitzer. This boat gun could be carried aboard small craft and was particularly useful in amphibious type landings. To demonstrate the advancements in ordnance made under his direction, in 1857 Dahlgren asked and was given command of the sloop of war Plymouth. He fitted it with his new guns and on 24 June 1857 left Washington bound on a training cruise. Plymouth returned home in November, having proved that large-caliber guns of the Dahlgren design could be safely fired aboard ship.

Dahlgren was at the Washington Navy Yard in April 1861 at the outbreak of the Civil War. The yard's commander Franklin Buchanan resigned to "go South," and Dahlgren was appointed to replace him. On 16 July 1862 he was promoted to captain, and two days later he took command of the Bureau of Ordnance. Dahlgren's reputation and his proximity to the White House often brought him in contact with President Abraham Lincoln, outside of the normal chain of command, which was looked upon with some suspicion by Dahlgren's peers. On 7 February 1863 he was promoted to rear admiral. Four months later, 24 June, Dahlgren was ordered to take command of the South Atlantic Blockading Squadron.

As commander of the Blockading Squadron, Dahlgren's chief goal was the capture of the port of Charleston. His predecessor, S. Francis Du Pont, had tried and failed in this attempt and was recalled as a result. During Dahlgren's command Charleston was kept under siege for almost two years. Pressed at sea by Dahlgren's forces and from the land side by William Tecumseh Sherman's advancing army, the Confederates evacuated Charleston 17-18 February 1865. Dahlgren was ordered to transfer his command of the squadron 9 June, when the force was integrated with the Northern Blockading Squadron and returned to its prewar status as the Atlantic Squadron.

Dahlgren returned to Washington. In September 1866 Dahlgren was ordered to take command of the South Pacific Squadron and left for his station on 1 December. He returned in July 1868 and was reassigned as chief of ordnance. In postwar Washington the bureau came under heavy criticism for lack of innovation. Feeling the pressure, Dahlgren asked to be reassigned. In August 1869 he was made commandant of the Washington Navy Yard, where he died.

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Peter Richards