Allen served as a member of the Vermont House of Representatives from 1810 to 1814, 1816 to 1817, 1822, and 1824 to 1826.[3] He moved to Burlington in 1828 and continued the practice of law.
While in Congress, Allen served as chairman of the Committee on Expenditures in the Department of the Treasury during the Twenty-third through Twenty-fifth Congresses. He was an unsuccessful candidate for reelection in 1838 to the Twenty-sixth Congress. After leaving Congress, Allen resumed the practice of law. He was a director of the Lake Champlain Steamboat Company.[6]
Personal life
Allen married Sarah Ann "Sally" Prentis Allen on December 4, 1804. They had eight children; Heman Jr., Lucius, George, Sarah, Charles Prentis, Joseph William, Julia, and James Heman.