George Brinton McClellan was born December 3, 1826, in Philadelphia, Pennsylvania. An excellent student, McClellan graduated from the US Military Academy in 1846 after attending the University of Pennsylvania.
After serving in Mexico under General Winfield Scott, McClellan taught at West Point and observed war in Europe. In 1861, he was named major general in the Union Army and replaced General McDowell as commander of the army of the Potomac after the disaster at Bull Run. McClellan soon became general-in-chief of the Union Army, but his pompousness and indecision regarding attacks and Confederate retreats resulted in the regrouping of Confederate forces that should have been routed, especially at Seven Points and Antietam. McClellan was also insubordinate toward President Lincoln and was openly disrespectful to him on several occasions.
Lincoln lost confidence in McClellan (as did the Union soldiers) and removed him as general-in-chief. McClellan entered politics during and after the war and became Governor of New Jersey in 1878. He died of a heart attack at the age of 58 in 1885.