Entered Williams College, 1800. Graduate Brown U., 1804.
Williamson was also an early historian of Maine. He moved to Bangor, then part of Massachusetts, in the first decade of the 19th century and established a law practice there in 1807. He became Bangor's postmaster (among other offices) in 1810.
During the War of 1812 he was present at the capture and sacking of Bangor by the British following the Battle of Hampden and, like all male residents of the town, was made to sign an oath declaring he would not take up arms for the remainder of the war. Following the war, in 1816, Williamson was elected to the Massachusetts State Senate representing the District of Maine, but became a force behind the movement for Maine statehood. In 1820, Maine separated from Massachusetts to become a state, and Williamson became the third President of the Maine State Senate.
In 1821, when the first governor, William King (governor) resigned, Williamson automatically succeeded him as he was president of the Senate. Williamson served as governor from May 29, 1821 to December 5, 1821. Williamson resigned as governor to serve in the U.S. House of Representatives, serving until 1823.
Williamson returned to his law practice in Bangor, also serving as Judge of Probate for Penobscot County till 1840. Williamson died in 1846 in Bangor. He is buried at Mt. Hope Cemetery.
Williamson was one of Maine's first historians, writing a 2-volume History of the State of Maine in the late 1830s. This stood as the standard reference on early Maine history for the rest of the 19th century.
(An authentic History of this State has been long and much...)
(Page 9to av. Oct. 7, Provincial Charter ot William and Ma...)
Member Massachusetts Senate, 1816-1819, Chairman of Commission on Eastern lands. Member United States House of Representatives from Maine, 17th Congress, 1821-1823.
Married Jemima Rice, June 10, 1806. Married second, Susan White, June 3, 1823.