Dr. Thornton discharged the duties of his important station ably and faithfully until his services were required upon the bench. On the 24th of December of the same year, he was again elected to Congress, and served until the 23d of January, 1777, when he retired finally from the national legislature, highly esteemed by all his associates, enjoying the full confidence and gratitude of his constituents, and the proud satisfaction of having performed his duty towards his country. For six years he served on the bench of the Superior Court, and was also Chief Justice of the Common Pleas; the combined duties of which rendered his task arduous. In 1779, he removed to Exeter, and the following year purchased a plantation upon the banks of the Merrimack river, where he sought that repose that his advanced age required. His friends, however, were not willing to excuse him from acting in public concerns, and induced him to serve as a member of the general court, and also in the state senate during the war, and for two years after its close. On the 25th of January, 1784, he was appointed a justice of the peace and quorum throughout the state, which was an important office under the original constitution of the state, but which was abolished in part, and abridged in jurisdiction, by the amendments of 1792. This he held to the day of his final retirement from all public duties; and, after 1785, he took no part in the politics of the day, but continued to afford salutary counsel on all important matters relative to the public weal, about which he was often consulted. During the controversy between his state and Vermont concerning a portion of disputed territory, he wrote several letters to those in power, urging the necessity of conciliatory measures, and an unconditional submission to the decision of Congress in the premises. They were highly creditable to him as an able patriot, a good writer, and a discreet man.