His practice became very extensive, and he was eminently successful, especially in the treatment of the Cynanche Maligna, or Throat Distemper, which first made its appearance in Kingston, with great fatality, in 1765.
Dr. Bartlett began his political career as Representative from Kingston, in the Legislature of New Hampshire, while an English colony.
He continued to fill various offices of trust, from this time to the year 1775, when he was elected to the Continental Congress, which met at Philadelphia in September of that year. In July, 1776, Congress declared the Colonies independent, and Dr. Bartlett was the first, after the venerable Hancock, to sign this instrument of American freedom.
In November, 1778, Dr. Bartlett returned home to attend to his domestic affairs, which had suffered greatly from his absence. About this time he was appointed Chief Justice of the Court of Common Pleas, and was transferred to the Superior Bench in November, 1782, and there officiated till he was appointed, in 1788, Chief Justice of the State. Judge Bartlett sustained, during this period, many offices not incompatible with his high judicial character, such as Counsellor, a member of the Convention to form a State Constitution, and was one of a Committee, with Judge Livermore and Gen. Sullivan, to revise the Laws of the State, and a member of the Convention to ratify the new Constitution.
In 1789, he was elected Senator to Congress, but his declining health, and the depression of spirits consequent upon the sudden death of his wife, early in that year, induced him to decline the duties of Senator, and to resign the office of Chief Justice.
The people, unwilling to lose his services, elected him President of the State, in 1790.
Dr. Bartlett took an active part in forming the New Hampshire Medical Society, and was elected, in 1791, its first President.
In 1792, he was chosen a member to revise the Constitution of New Hampshire, in which the title of President was dropped, and that of Governor substituted, and he was the first Chief Magistrate with the title of Governor. About this time, he received the honorary degrees of M. A. and M. D. from Dartmouth College.
Gov. Bartlett filled all these stations with general satisfaction, without ostentation; administering the laws in a mild yet decisive manner, and setting forth the example of true republicanism.