George Brinton McClellan was born in Philadelphia, Pennsylvania, on 3 December 1826; attended preparatory schools and left the University of Pennsylvania to accept an appointment to the United States Military Academy, graduating in 1846; served with distinction as an engineer officer under Generals Zachary Taylor and Winfield Scott in the Mexican War, 1847, receiving brevets to first lieutenant in August and captain in September; was assistant instructor in practical military engineering at West Point, 1848?1851; was assistant engineer for the construction of Fort Delaware; participated in the Marcy expedition to explore the sources of the Red River, Texas, 1852; was chief engineer of the Department of Texas, 1852; conducted a survey for the projected Northern Pacific Railroad over the Cascade Mountains; was promoted to captain, March 1855, and assigned to the new 1st Cavalry Regiment; visited Europe to study foreign military systems and observe Crimean War operations, 1855?1856; designed and secured adoption of the McClellan saddle; resigned from the Army to become chief engineer (1857?1858) and vice president (1858?1860) of the Illinois Central Railroad; married Mary Ellen Marcy, 1860; was president of the Ohio and Mississippi Railroad, 1860?1861; was appointed major general of Ohio Volunteers, April 1861; was appointed major general in the Regular Army and commander of the Department of the Ohio, May 1861; cleared Confederate troops from western Virginia; successively commanded the Division, Department, and Army of the Potomac, July?November 1861; was commanding general of the Army, 1 November 1861?11 March 1862; was relieved of overall command to lead the Army of the Potomac in the Peninsular Campaign, including the siege of Yorktown, the battle of Fair Oaks, and the Seven Days? Battles, 1862; commanded the Washington defenses, September 1862; commanded the Army of the Potomac in the Maryland operations at South Mountain and Antietam and was placed on inactive status by President Lincoln for his failure to pursue Lee after Antietam, 1862?1864; resigned his commission to run unsuccessfully against Lincoln for the Presidency, 1864; spent three years in Europe; declined the presidency of two colleges and appointment as comptroller of New York City; was chief engineer of New York City?s Department of Docks, 1870?1872; was governor of New Jersey, 1878?1881; was on the Board of Governors of the National Home for Disabled Soldiers, 1881?1885; died in Orange, New Jersey, on 29 October 1885.