Civil War Union Brigadier General. Born is Swedesboro, New Jersey, he was appointed to the United States Military Academy in West Point, New York by New Jersey Congressman Nathan T. Stratton, whom he was working for as a clerk in the Congressman’s business. He graduated in 1858, placing sixteenth in a class of twenty-seven, eleven of which would fight for the Confederacy during the Civil War, including Confederate General Bryan M. Thomas. Posted as a 2nd Lieutenant first with the 2nd United States Infantry regiment, then the 9th United States Infantry regiment, he served in garrison duty in New York City, New York, then in escort duty in the Pacific Northwest territories of Oregon and Washington. When the Civil War began he was recalled east, where he was assigned to train and drill volunteer Union troops assembling in Ohio. Promoted to Captain in the newly formed 15th United States Regular Infantry on October 24, 1861, he was commissioned as Colonel of Volunteers a month later on November 11, 1861 and placed in command of the 65th Ohio Volunteer Infantry. He regiment was assigned to the 21st Brigade of the 6th Division of the Army of Ohio, which was commanded by Major General Don Carlos Buell. His brigade commander was future United States President Brigadier General James A. Garfield. At the April 1862 Battle of Shiloh in Tennessee, his men were part of the force that arrived the day after the battle began, and helped push the Confederates back after gains they made at the beginning of the engagement. He led his men through the April-May 1862 Siege of Corinth, Mississippi, then in June 1862 took command of his brigade when General Garfield was prostrated with illness and returned to his home to recover. He led the brigade in the October 1862 Battle of Perryville, Kentucky and, after the army he was in was re-designated as the Army of the Cumberland, the December 1862-January 1862 Battle of Murfreesboro, Tennessee. He continued in brigade commander through 1863 during operations in Tennessee under Major General William S. Rosecrans, and was praised for his unit’s performance at the September 1863 Battle of Chickamuaga. His men greatly aided Major General George Thomas' staunch defense on Snodgrass House Hill on the second day of the battle, which saved the Union Army from disaster. Promoted to Brigadier General, US Volunteers after the engagement, his commission was dated to September 20, 1863. His men fought in the battles in and around Chattanooga, Tennessee, and were part of the relief force that helped lift the Confederate siege of Knoxville. In the Spring of 1864 his men were part of the Union operations under Major General William T. Sherman that pursued the Confederate Army of Tennessee. On May 7, 1864 his brigade worked their way up the steep cliffs of Rocky Face Ridge near Dalton, Georgia, and captured the position despite heavy Confederate fire and difficult, rocky terrain. General Harker held the heights until May 13 despite Confederate efforts to drive them off. His brigade was selected as one of the three Union assaulting forces on June 27, 1864 during the Battle of Kennesaw Mountain, near Marietta, Georgia. There he led his men while riding a white horse in the center attack on Confederate positions that became known as Cheatham Hill. The assault faltered due to very rough, mountainous terrain, and because of well-positioned Confederates who were behind strong fortifications. While rallying his men he was shot off his horse, and, after being brought behind Union lines, died later in the day. His remains were sent back to his hometown of Swedesboro, and after the war the veterans of his brigade erected a monument to him over his grave site.