In 1820 was appointed chief commissioner of insolvent debtors, which office he held until 1821, when he was elected to the state senate, serving five years. He was re-elected and resigned in the second year of that term. In 1845 he was chosen a Senator in Congress. He remained there until 1848, when he resigned to accept the post of Attorney-General of the United States. In 1862 he was again elected a senator in congress from Maryland for the term commencing in 1863 and ending in 1868. He was the US Minister to England from 1868 to 1869.
Johnson, Rossiter (ed.), The Twentieth Century Biographical Dictionary of Notable Americans, 10 vols., Boston, 1904, vol. 6; Who Was Who in America, Chicago, 1964, p. 281.