Dalton was not significantly involved in politics until 1774, when the tensions of the
American Revolution were rising but the
American Revolutionary War had not yet started. He was elected to the
Massachusetts Provincial Congress and the Newburyport board of selectmen in 1774, and was an active proponent of independence after the war broke out. His contributions included provisioning of ships from his merchant fleet to the
Penobscot Expedition of 1780. Dalton served as a member of the
Massachusetts House of Representatives from 1782 to 1785, and served as
its speaker in 1784. He served as a
Massachusetts state senator from 1786 to 1788. Dalton was elected to the
Continental Congress in 1783 and 1784, but did not attend. He was elected as a delegate to the state convention on the adoption of the
United States Constitution, in which he advocated for its adoption. In 1788 he was elected as one of the state's first
United States Senators, along with
Caleb Strong. Strong won the draw for the longer of the two terms, leaving Dalton with a short two-year term. He served from March 4, 1789, to March 3, 1791. In the 1791 election (US Senators were then chosen by vote of the state legislature), Dalton ran a distant fourth against
George Cabot, the eventual victor, and others. In 1801 he was appointed by President Thomas Jefferson as the last commissioner of the Federal City, which by then had been named Washington in the District of Columbia. He filled the seat vacated by William Cranch who was appointed to the bench in the new capitol and served for a little over a year until the Board of Commissioners of the Federal City was disbanded in 1802. ==Later life==