Although Thomas Johnson received no formal education growing up in western Maryland, he read for the bar under the tutelage of a local attorney and entered the bar at age 28.
Johnson, a close friend and business associate of George Washington, was elected a member of the Continental Congress. Johnson placed Washington's name in nomination for commander-in-chief of the Continental Army.
Johnson served three terms as governor of Maryland. He then served in the Maryland House of Delegates; and he worked energetically toward ratification of the new federal constitution. Thereafter, he served as chief judge of the Maryland General Court. His old friend, Washington, lured him to federal service with an appointment to the Supreme Court.
Johnson found circuit-riding an ordeal; he resigned after only 14 months on the Court. During his brief tenure, Johnson wrote only a single short opinion out of a total of four cases that were before the Court that term.