McClellan, George Brinton, 1826–85, Union general in the American Civil War, b. Philadelphia. After graduating (1846) from West Point, he served with distinction in the Mexican War and later worked on various engineering projects, notably on the survey (1853–54) for a Northern Pacific RR route across the Cascade Range. Resigning from the army in 1857, he was a railroad official until the outbreak of the Civil War. In May, 1861, McClellan was made commander of the Dept. of the Ohio and a major general in the regular army. He cleared the western part of Virginia of Confederates (June–July, 1861) and consequently, after the Union defeat in the first battle of Bull Run, was given command of the troops in and around Washington. In November he became general in chief. The administration, reflecting public opinion, pressed for an early offensive, but McClellan insisted on adequate training and equipment for his army. In Mar., 1862, he was relieved of his supreme command, but he retained command of the Army of the Potomac, with which in Apr., 1862, he initiated the Peninsular campaign. The collapse of this campaign after the Seven Days battles was charged by many to his overcaution. In Aug., 1862, most of McClellan's troops were reassigned to the Army of Virginia under John Pope. After Pope's defeat at the second battle of Bull Run, McClellan again reorganized the Union forces, and in the Antietam campaign he checked Robert E. Lee's first invasion of the North. He was slow, however, to follow Lee across the Potomac and in Nov., 1862, was removed from his command. In 1864, McClellan was the Democratic candidate for President, although he rejected the party's peace platform. McClellan's candidacy caused the administration much uneasiness, but President Lincoln was reelected by a substantial majority. McClellan resigned from the army on the day of the election and afterward traveled extensively with his family in Europe. He was later chief engineer of the New York City department of docks and was governor of New Jersey (1878–81). Despite his faults "Little Mack" was an able general and was loved and trusted by his men of the Army of the Potomac. He wrote McClellan's Own Story (1887) in defense of his military record.
See The Civil War Papers of George B. McClellan: Selected Correspondence, 1860–1865 (ed. by S. W. Sears, 1989); biographies by W. S. Myers (1934), H. J. Eckenrode and B. Conrad (1942), and W. W. Hassler, Jr. (1957); T. H. Williams, McClellan, Sherman, and Grant (1962).