 George Brinton McClellan was born in Philadelphia , the son of a prominent surgeon , Dr. George McClellan , the founder of Jefferson Medical College . His father 's family was of Ulster Scots heritage . His mother was Elizabeth Sophia Steinmetz Brinton McClellan ( 1800 – 1889 ) , daughter of a leading Pennsylvania family , a woman noted for her " considerable grace and refinement " . The couple had five children : a daughter , Frederica ; then three sons , John , George , and Arthur ; and finally a second daughter , Mary . McClellan was the great @-@ grandson of Revolutionary War general Samuel McClellan , of Woodstock , Connecticut . He attended the University of Pennsylvania in 1840 at age 13 , resigning himself to the study of law . After two years , he changed his goal to military service . With the assistance of his father 's letter to President John Tyler , young George was accepted at the United States Military Academy in 1842 , the academy having waived its normal minimum age of 16 . 
