Joseph King Fenno Mansfield was the son of Henry and Mary (Fenno) Mansfield. He was born December 22, 1803 in New Haven, Connecticut He was a lineal descendant of Richard Mansfield who came from Exeter, England, in 1639, and a nephew of Jared Mansfield, professor at the United States Military Academy from 1812 to 1828, and a first cousin of Edward Deering Mansfield.
Joseph Mansfield became a cadet at the Military Academy in 1817.
On graduation of the Military Academy in 1822 was commissioned second lieutenant and assigned to the Corps of Engineers. Until the Mexican War he was engaged mainly in the construction of the coast defenses of the South Atlantic states and was specially charged with the construction of Fort Pulaski at the mouth of the Savannah River. He was promoted to first lieutenant in 1832 and captain in 1838. During the Mexican War, he was chief engineer of the army under General Taylor and as such served with great distinction. At the beginning of operations he designed and constructed Fort Brown on the Rio Grande opposite Matamoras and took part in its defense. George Gordon Meade, then a subaltern in this army, wrote in a letter that Mansfield "had gained for himself great credit for the design and execution of the work and still more for his energy and bravery in its defence". At Monterey, he made the preliminary reconnaissance on which the plan of the battle was based and conducted one of the columns of attack. He was equally active in reconnoitering the ground and selecting the positions for the troops in the battle of Buena Vista. After the war he was again engaged as a captain in the construction of coast defenses until 1853 when, upon the recommendation of Secretary of War Jefferson Davis, who had also served in Taylor's army, he received an unsolicited promotion to colonel and inspector-general of the army. Under his new commission he traveled extensively, inspecting frontier posts in Texas, New Mexico, California, and Oregon. Shortly after the outbreak of the Civil War he was commissioned brigadier-general in the Regular Army and assigned to the command of the Department of Washington, which included the capital and surrounding territory. It was on his recommendation that the heights on the south bank of the Potomac opposite the city were promptly seized and fortified. When his department was merged into the Department of the Potomac under McClellan, he was assigned to command under General Wool at Fort Monroe and in 1862 took part in the occupation of Norfolk and Suffolk, Va. , being commissioned major-general of volunteers in July. When McClellan reorganized the Army of the Potomac after the Manassas Campaign, Mansfield was recalled from Suffolk where he was in command, and assigned to the command of the XII Corps. He joined the army two days before the battle of Antietam and was mortally wounded in that battle, September 17, 1862, while reconnoitering the enemy's position as his corps was coming into action.
In the Mexican War he served as Chief Engineer in General Zachary Taylor's Army, participating in the Battles of Fort Brown, Monterrey and Buena Vista, and receiving brevet promotions up to Colonel, US Regular Army for his services. For gallant and distinguished services in the defense of Fort Brown he received the brevet of major, for gallant and meritorius conduct in the battles of Monterey and Buena Vista he received the brevets of lieutenant-colonel and colonel. Six months after his death he was posthumously promoted to Major General, US Volunteers.
On September 25, 1838, he had married Louisa Maria Mather, the daughter of Samuel and Catherine (Livingston) Mather. They had two daughters and two sons, one of whom, Samuel Mather Mansfield, became a brigadier-general in the Corps of Engineers.
14 June 1808 - 22 Febraury 1880
23 March 1841 - 22 June 1863
1 May 1850 - 8 January 1918
4 October 1843 - 15 July 1844
31 March 1845 - 14 January 1918
25 September 1839 - 18 February 1928
March 17, 1842 – September 19, 1863 Is best known for having fought and died at the Battle of Chickamauga in Georgia, during the American Civil War.
