In 1759, captain Whipple relinquished his oceanic pursuits, and commenced the mercantile business in Portsmouth, New Hampshire. He also married Miss Catharine Moffat, and entered upon a new scene of life. During his numerous voyages he had become celebrated as a skilful navigator and a judicious commanding officer. He had carefully treasured a large fund of useful knowledge by close observation, attentive reading, and by mingling, when in port, with none but intelligent and good company. He had listened, both in England and America, to the unwarranted pretensions of the former, and the increasing complaints of the latter. He had made himself familiar with the chartered rights of his own country, and with the usurpations of the crown over his fellow citizens. He was prepared to take a bold stand in favour of freedom. He took a conspicuous part in public meetings, and was chosen one of the committee of safety. He rose rapidly in public estimation, and the former cabin boy became a leading patriot. In January, 1775, he represented Portsmouth in the Provincial Congress, convened at Exeter, for the purpose of choosing delegates for the Continental Congress. On the 6th of January of the following year he was chosen a member of the provincial council of New Hampshire, and on the 23d of the same month, a delegate to the national legislature at Philadelphia, of which he continued a distinguished, active, and useful member, until the middle of September, 1779. He was present at the adoption of the Declaration of Independence, and affixed his name to that sacred and bold instrument with the same fearless calmness with which he would have signed a bill of lading.
He was emphatically a working man, and from his extensive knowledge of business, rendered himself highly useful on committees. As a member of the marine and commercial committees, his practical knowledge gave him a superiority over his colleagues. He was also appointed one of the superintendents of the commissary and quartermaster department, and did much towards correcting abuses and checking peculation. He was untiring in his industry, ardent in his zeal, philosophic in his views, pure in his purposes, and strong in his patriotism. When he finally retired from Congress to serve his country in another and more perilous sphere, he carried with him the esteem and approbation of all his co-workers in the glorious cause of liberty. On his return to his constituents he was hailed as a SAGE, a PATRIOT, and a HERO.