John Baillie McIntosh was born on June 6, 1829 in Florida. He was the son of Col. James Simmons McIntosh, United States Army, and the brother of James McQueen McIntosh, later a brigadier-general in the Confederate army. His mother, Eliza (Matthews) Shumate McIntosh, was the daughter of James Matthews of Brooklyn, New York.
The last of an illustrious fighting family, John entered the navy during the Mexican War and served aboard the U. S. S. Saratoga as a midshipman. Upon his return home after the war, he learned of his father's death in Mexico as the result of wounds received in the battle of Molino del Rey. He thereupon resigned from the navy and went to live with an uncle at New Brunswick, New Jersey. For the next decade, McIntosh engaged in business with his father-in-law. When the Civil War began, he declared for the preservation of the Union and applied for a commission in the Regular Army, notwithstanding the many family and social influences tending to enlist his sympathies with the South. He considered as a blot on his family honor the resignation from the Federal service of his brother, who had been educated at West Point and now took up arms against the government. In June 1861, he entered the Federal service as a second lieutenant of cavalry. Serving in the Shenandoah Valley in 1861 and later with the Army of the Potomac, he at once drew the attention of his commanders and was frequently commended in orders. In July 1862, he was assigned temporarily to the command of the 95th Pennsylvania Volunteers, whose colonel had been killed. For gallant and meritorious services at White Oak Swamp (August 1862) he was brevetted major; he participated in the battles of South Mountain and Antietam, and in November 1862 was appointed colonel of the 3rd Pennsylvania Cavalry. When the Union cavalry was reorganized by Gen. Alfred Pleasanton in the spring of 1863, McIntosh was given the command of a brigade, with which he distinguished himself at Kelly's Ford (March 1863). He fought at Chancellorsville and played a significant role in the cavalry fighting of the Gettysburg campaign, demonstrating that as a brigade commander he had no superior. While recuperating from a fall from a horse, he was placed in charge of the Cavalry Depot in Washington. Returning to the command of his brigade in May 1864, he took part in the great cavalry operations of that year, ending with the battle of Winchester, where he received wounds necessitating the amputation of his right leg. He received in succession every brevet grade from major to major-general for bold, valiant, and gallant action under fire. After the war, he was commissioned a lieutenant colonel in the Regular Army upon the special recommendation of General Grant. He commanded the 42nd Infantry 1866-67, was deputy governor and governor of the Soldier's Home at Washington 1867-68, and superintendent of Indian affairs in California, 1869-70. He was retired in 1870 with the rank of brigadier-general, and made his residence in New Brunswick, New Jersey, where he took an active interest in public affairs.
At the start of the Civil War, McIntosh joined the Union Army as a Second Lieutenant in the 2nd US Cavalry. He fought in the Peninsula and Maryland campaigns and was made Colonel of the 3rd Pennsylvania Cavalry, in November, 1862. He commanded the 2nd Brigade Cavalry Corps at Kelly's Ford, Chancellorsville, Gettysburg and was promoted Brigadier General in July, 1864. During the 3rd Battle of Winchester in September 1864, he was wounded, which resulted in the loss of a leg and ended his field duties. Following the war, he remained in the military serving as governor of Soldier's Home in Washington DC and superintendent of Indian affairs.
McIntosh was a born fighter, a strict disciplinarian, a dashing leader, and a polished gentleman. He represents the highest type of volunteer soldier.
In 1850, McIntosh married Amelia Stout. One child, a daughter, was born to this union.
