In September of that year, Messrs. Clymer and Stockton were sent by Congress to regulate the northern army and to confer with Washington in making arrangements for future action. In December of the same year Congress retired to Baltimore in consequence of the threatened approach of the British army, then spreading consternation, destruction and death through New Jersey. Mr. Clymer was one of the committee left in Philadelphia to superintend the public interests and brave the perils that were rolling onward like a tornado. He was faithful in the discharge of every duty, devoting his time and fortune to the advancement of the glorious cause he had espoused. He was returned to Congress the next year, and in April was again appointed upon a committee to repair to the army and confer with Washington upon all subjects that required their attention, which were neither few nor small. In the autumn of that year an additional momentum was given to the patriotism of Mr. Clymer. He had removed his family and goods to Chester county, and immediately after the defeat of the Americans at Brandywine, the tories led the British to his house; his family escaped, but his property, to a large amount, was totally destroyed. This sacrifice at the altar of freedom seemed to strengthen his political faith and impart fresh vigour to his exertions.
In December, 1779, he was one of a board of commissioners sent by Congress to Fort Pitt, to counteract, if possible, the hostility of the savages, who were committing murders upon the western frontiers of Virginia and Pennsylvania, and to effect, if practicable, a treaty with the several tribes, and if unsuccessful in the accomplishment of these designs, to make arrangements for offensive operations. The mission was boldly executed, principally by Mr. Clymer alone, who narrowly escaped the tomahawk during his absence. The commissioners returned in April and reported the necessity of carrying the war into the Indian country. During the next year Mr. Clymer was not in Congress, but devoted his time in raising loans and supplies for the army, then destitute of almost every necessary of life and of the munitions of war. In 1780, he was again elected to the national legislature and served until November of the ensuing year, when he and John Nixon were appointed to organize the Bank of North America, which was instrumental in reviving the prostrate credit of the government. In May, 1782, he was associated with Mr. Rutledge on a mission through the southern states, for the purpose of inducing them to meet more promptly the requisitions of Congress for supplies. During the entire period of the revolution he devoted his whole time to the service of his country, and discharged every duty assigned him to the entire satisfaction of his constituents and colleagues. He stood high as an able and faithful co-worker in the vineyard of liberty, and retired from the field when the harvest was ended covered with the honours of enduring fame. At the close of the war he removed to Princeton, for the purpose of resting from his toils and educating his children. The ensuing year his services were requested in his native state, and he returned to Philadelphia. He was elected to the Pennsylvania legislature, and contributed largely in divesting her old constitution and laws of the obnoxious branches of tyranny that were still attached to them. He introduced the amelioration of the penal code and was the originator and warm advocate of abolishing death in all cases, except murder in the first degree. He was the father of the much admired penitentiary system of that state, which has but recently been organized fully upon the plan proposed by him—that of solitary confinement at hard labour. It may not be known to the young reader, that in former times, prisoners, after conviction, were compelled to labour in chains often in the most public places. The superiority of solitary confinement over all other modes of punishment has been fully demonstrated, and is in a course of adoption throughout the civilized world. The arguments of Mr. Clymer in favour of these philanthropic measures manifested a deep and thorough knowledge of human nature, and were based upon the firm pillars of equal justice, lucid reason and sound policy. He devised and prepared the humane report of the committee that remodelled the penal code of Pennsylvania, which has been fully and successfully tested, and stands an admired monument of judicial reformation, and an enduring praise to the name of its author.