Joseph King Fenno Mansfield

By John T. Marck

Mansfield was born in New Haven, Connecticut on December 22, 1803, and entered West Point at the age of thirteen, graduating five years later in 1822. Over the next twenty years, Mansfield served as an engineer officer, building defenses along the Southern Coast. During the Mexican War, he served with bravery under General Zachary Taylor as his chief engineer, earning him promotions of major, lieutenant colonel, then colonel. In 1853, U.S. Secretary of War, Jefferson Davis (not to be confused with the Confederate president), who also served under Zachary Taylor, recommended Mansfield for a promotion to staff colonel in the inspector's general's office. Accepting this post, he remained here until the Civil War began.

On April 28, 1861, Mansfield was given a command in the Department of Washington. One month later he was promoted to brigadier general, and was active with his troops in strengthening positions on the Virginia side along the Potomac River. Mansfield stayed in this command until March 1862, when he then served under Major General John E. Wool at Fort Monroe. On September 12, 1862, he assumed command of the XII Corps, Army of the Potomac, who at this time were in Frederick, Maryland.

With the XII Corps, Mansfield was in pursuit of the Army of Northern Virginia under the command of General Robert E. Lee. Leaving Frederick, they arrived at Sharpsburg on September 17. During the Battle of Antietam this day, Mansfield led his XII Corps into battle. Two hours into the battle, Mansfield crossed the forty-acre cornfield, leading his troops into the East Woods. As he and his men approached the edge of the woods at the tree line, the Confederates, who were hiding there, opened fire. The men of the XII Corps momentarily believed that the men in the woods were Union soldiers, who mistakenly fired. Consequently, they hesitated in returning fire, while Mansfield rode closer. Without warning, the Rebels fired another volley into the XII Corps. With this, Mansfield was shot in his stomach. He was removed from the field of battle and taken to a field hospital, where he lived less than a day, dying on September 18, 1862.

Joseph Mansfield was promoted posthumously to major general on March 12, 1863, retroactive to July 18, 1862.

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