Marion was elected to the state senate in 1781 even before the war had ended and was at Jacksonboro on January 8, 1782, for the General Assembly. His brigade was still given the task of protecting the area. On January 10, he wrote to Colonel Peter Horry to take command, but by January 24th, Marion had to take leave of the assembly to resume command. Horry and Colonel Hezekaih Maham, commander of the brigade's dragoons, had a rivalry going, so both were turning their responsibilities over to their subordinates.
Colonel Benjamin Thompson led a 700-man force from Charleston and scattered Marion's divided brigade. Marion arrived in time to rally his men and launch a counterattack, but some of his more inexperienced men led to his counterattack being turned back at Wambaw Bridge. Marion withdrew to one of his camps at Cantey's Plantation disheartened by the performance of his subordinates in his absence. In the summer of 1782, Marion again patrolled the area east of the Cooper River. On August 29, he ambushed 200 men under Major Thomas Fraser at Fair Lawn after they were drawn into a trap, but the British did capture an ammunition wagon and Marion had to retreat. It would be his last action of the war.
After the Revolutionary War: 1782-1795
Marion was reelected to the State Senate in 1782 and 1784. He supported a policy of leniency toward Tories and opposed the Confiscation Act that would have taken property away from Tories. In appreciation for his service during the war, the state legislature appointed him commander of Fort Johnson at a substantial salary. That salary helped him rebuild his plantation, which had been all but destroyed during the war.
On April 20, 1786, he married his wealthy cousin, Mary Esther Videau and settled at Pond Bluff. He was a representative at the Constitutional Convention in 1790 where he voted for a federal union. In 1790, he also resigned his post at Fort Johnson. In 1791, he was elected to fill an unfinished term in 1791. After the state officially joined the union, Marion retired from public office and remained at Pond Bluff. He died on February 27, 1795. He was bured at Belle Isle Plantation.
