JOHN MERCER PATTON was born in Fredericksburg, Virginia. After studying briefly at Princeton, he graduated from medical school at the University of Pennsylvania but did not practice medicine. Instead, he went on to study law in Fredericksburg and practiced law there. Elected to the U.S. House of Representatives to fill a vacancy, he was reelected to four consecutive terms. He returned to Richmond and was elected to the Virginia Council of State, serving from 1838 to 1841. As senior member of the Council, Patton assumed the office of governor upon the resignation of Thomas W. Gilmer. He served for only twelve days, however, until the state legislature chose his successor. He returned to the practice of law and was appointed to revise and condense the Civil Code of Virginia in 1846, after which he prepared a new code in 1849. He was also appointed to the Board of Visitors of the Medical College of Virginia in 1854, serving as its president until his death.