Civil Union Navy Officer. He was an naval officer and mining engineer, was the eldest son of Rear Admiral John Adolphus and Mary Clement (Bunker) Dahlgren. He studied steam engineering and at the outsbreak of the civil war in the United States entered the naval service and served as an officer continuously through the war. He was serving on board the U.S.S. San Jacinto, Captain Wilkes, when Mason and Slidell were captured in 1861. He took part, under Rear Admiral David A. Porter, in the passage of the forts and the capture of the city of New Orleans in 1862 and in the passage of the batteries and the investment and capture of Arkansas Post and Vicksburg, 1863. He commanded the siege battery of IX inch Dahlgren shell-guns at Vicksburg, which destroyed the powerful batteries inside the beleaguered city. He was also fleet ordnance officer on the iron-clad squadron commanded by his father in front of Charleston and in the North Atlantic blockading squadron in 1864 and senior watch officer of the U.S.S. Onondaga, which protected the right flank of Grant's army at Petersburg. He had been executive officer of the U.S. steamer Gettysburg, 7 guns, in the attack and capture of Fort Fisher in 1865. He received honorable mention in orders and reports, and for his services was promoted first lieutenant and captain during the progress of the war. Upon tendering his resignation in 1865 he was asked by the secretary of the navy to reconsider and accept service in the regular establishment. He declined the honor and engaged in mining and mechanical engineering in the far west and Mexico. He was married in 1867 to Augusta Smith, great great granddaughter of the Hon. Henry Wisner, delegate to the Continental congress from Orange county, N.Y., and a Revolutionary patriot. After twenty-five years residence in the far west, he removed to the east, residing at Nantucket, Massachusetts and at Trenton, New Jersey alternately. In 1898 he commanded a battalion of the New Jersey naval reserves and furnished the officers and crews for two ships in the Spanish war, the U.S.S. monitor Montauk and the U.S.S. Resolute. He named one son John Adolph for his father, and one Ulric, for his brother, a colonel of cavalry killed before Richmond. He was elected a fellow of the American geographical society and a member of the Long Island historical society, the G.A.R., the Loyal legion, the Naval order and the Masonic order. He published: Historic Mines of Mexico (1883); The Dahlgren Gun and Its Services during the late Civil War (1889) and numerous historical, biographical and technical papers. Source: American Biographical Library, The Twentieth Century Biographical Dictionary of Notable Americans, Volume 3