George Washington attested that Robert Hanson Harrison discharged his duty "with conspicuous abilities – That his whole conduct during all the interesting periods of the war has been distinguished marked by the strictest integrity and the most attentive & faithful services while by personal bravery he has marked his conduct upon many occasions been distinguished on sev[era]l occasions" [8] Returning to Maryland, Robert Hanson Harrison was appointed Chief Justice of the General Court of Maryland on March 12, 1781.

[9] During the war, Harrison's court considered property confiscation cases for individuals accused of disloyalty to the United States.

Despite being considered a highly capable judge, he declined appointments to higher courts because of failing health, including Chancellor of Maryland.

September 24, 1789, President George Washington nominated Harrison as an associate justice on the newly established United States Supreme Court.

Washington's friend Dr. James Craik urged him to send Harrison a personal appeal[clarification needed], believing "A Letter from you…would I am convinced act more powerfully upon him than all the Anodynes in an Apothecarys Shop".

[13] Harrison agreed to accept, and began the trip to New York City, then the temporary national capital.