Born and raised in Harrisville, Virginia (now part of West Virginia), Harris originally set out to be a teacher, but changed career paths to study medicine. He first attended Marietta College but later received his medical degree from Louisville Medical College in 1843. Harris returned to Virginia to practice medicine until 1861 when he closed his practice and took a commission as a Union officer when the Civil War began.

During the war, Harris commanded the 10th West Virginia Volunteer Infantry Regiment in the Shenandoah Valley, then a brigade and division under General Philip Sheridan. During campaigns of 1864 Harris was brevetted to brigadier general for service at the Battle of Cedar Creek on October 19, 1864.

He was transferred to the Army of the James and took command of a division of reinforcements from the Department of West Virginia attached to the XXIV Corps. He received a full promotion to brigadier general in March 1865 and a brevet promotion to major general for service at the battle of Fort Gregg on April 2, 1865. His troops were among those directly responsible for cutting off Robert E. Lee’s line of retreat at Appomattox Courthouse.  Following the Confederate surrender at Appomattox, Harris served on the military commission which tried the Lincoln Conspirators.

After the war, Harris elected to the West Virginia legislature and was appointed an adjunct general in the state militia and the U.S. pension agent for Wheeling, West Virginia. He resumed his medical practice until his retirement in 1885.