He was appointed Attorney-General of Maryland on October 18, 1806, to succeed John Thomson Mason, his predecessors in that office having also included Luther Martin and William Pinkney.
[1] Chief Justice Roger B. Taney, in his Autobiography, mentions John Johnson along with Luther Martin, Philip Barton Key, John Thomson Mason, Arthur Scharff, James Winchester as a leader of the bar when he went to Annapolis to study law in the first decade of the last century.
[1] Upon the death of William Kilty, Johnson was the sole candidate considered for the office of Chancellor of Maryland.
[1] On January 9, 1794, he married Deborah (née Ghiselen) Johnson (1773–1847), the daughter of Reverdy Ghiselin.
Together, they were the parents of: He died at Hancock, Maryland on July 30, 1824 of fever while in discharge of his duties in the western part of the State.