Mifflin was mixed up in the “Conway Cabal,” but in after years he explained his position, and it would seem to prove the intensity of his devotion to the struggle in which he had staked fortune and life itself.
In 1783 General Mifflin was elected a member of Congress, and had the satisfaction of being President of that body, when General Washington, December 23, 1783, resigned his commission into its hands. Mifflin made an eloquent reply.
General Mifflin was a member of the Assembly of Pennsylvania which met in 1785; also of the convention which sat in 1787 and framed the Constitution of the United States.
In 1788 he was chosen a member of the Supreme Executive Council, and upon the retirement of Franklin, he was elected President.
General Mifflin was the president of the convention that framed the State Constitution of 1790, and he and General Arthur St. Clair were the two candidates for Governor. Mifflin triumphed and was continued in office for that and the two succeeding terms.
Governor Mifflin was very efficient in quelling the Whisky Insurrection of 1794, and personally commanded the troops from Pennsylvania.
His last official communication as Governor was made December 7, 1799. It contained his farewell sentiments on taking leave of office and was received with every manifestation of respect by the Assembly.
He was elected to the Assembly and took his seat, but did not long survive. He died during a session of the House, then sitting in Lancaster, on January 21, 1800. His decease was noticed with becoming ceremonies, resolutions being adopted expressive of the high sense entertained for him as a soldier and statesman, authorizing his interment at the public expense and providing for the erection of a monument to his memory.
“Thus ended,” says Dr. Rawle, “the checkered life of Thomas Mifflin—brilliant in its outset—troubled and perplexed at a period more advanced—again distinguished, prosperous and happy—finally clouded by poverty and oppressed by creditors. In patriotic principle never changing—in public action never faltering—in personal friendship sincerely warm—in relieving the distressed always active and humane—in his own affairs improvident—in the business of others scrupulously just.”