General Matthews was not exchanged until the close of the war. He then joined the Southern army under General Greene, and commanded the Third Virginia Regiment. While in the South, he bought a tract of land on Broad River, known as the Goose Pond. He settled there with his family in 1784. The fame he had won as a soldier made General Matthews at that time the principal man in Georgia. He was elected governor in 1786. When his term expired, he was sent to Congress. In 1794-95 he was again made governor; and it was at this time, that, contrary to all expectations, he was prevailed on to sign the Yazoo Act. No charge of corruption was ever made against him. No thief or swindler was ever bold enough to try to bribe such a high-spirited and fearless man. But excitement in the State ran so high, that General Matthews was ruined so far as his influence was concerned. He left Georgia, and never afterwards made the State his home for any long period. In 1811 a lot of runaway negroes, ruffians, and lawless men congregated in Florida in such numbers that they were able to get control of affairs. They formed a government of their own, and then petitioned the United States to make Florida one of their territories. President Madison appointed General Matthews the agent of the United States to negotiate with the "constituted authorities" for the annexation of Florida. General Matthews made a treaty with those who were in control of Florida; but Spain protested, and the President finally declared that the treaty had not been made with the "constituted authorities." General Matthews was not a learned man (he knew nothing of books), and he could not understand the fuss that was made over the term "constituted authorities." He became very angry with the President, said that that officer had a cowardly fear of Spain and Great Britain, and declared that he would go to Washington to "thrash" the President. He actually set out on that errand; but the fatigue and exposure which he had experienced in Florida, and the high state of excitement under which he labored, threw him into a fever while he was on his journey to Washington, and he died in Augusta in March, 1812.