Harry Dwight Sisson was born on January 9, 1863 in Stockbridge, Massachusetts. He moved to Pittsfield, Massachusetts in 1882.

His father, Henry D., enlisted in Co. E,  49th Massachusetts Infantry on September 15, 1862 and was elected a 2nd Lt. of his Company. He acted as its Captain during the Fort Hudson campaign. He mustered out on September 1, 1863 as a 2nd Lt.

Harry was a charter member of the General William F. Bartlett Camp No. 108, Pittsfield joining on March 28, 1890, and served as its first Captain. He was Massachusetts' Division Commander in 1896. At the 1919 National Encampment, P. A. Barrows of the Nebraska Division was also nominated for Commander-in-Chief, but he withdrew his name giving Brother Sisson the uncontested win. Harry was also a Secretary of the 49th Regiment Association.

In 1892, 1893, and 1894 he served as Tax Collector and from 1896 to 1900 as an Assessor for the city. For 1903 and 1904 he was the city's Mayor. Just after being nominated by the Republicans of the Third Berkshire District as their Representative in the Massachusetts House for another term, he died. He had served for 10 years (1929 – 1938).

Harry was a bookkeeper for the Kellogg Shoe Co. and the Terry Clock Co., a traveling representative for the Berkshire Life Insurance Co., he owned a paper box manufacturing company, was Editor of the Connecticut Western News, and a retired auto dealer with 26 years of experience.

He was a 32nd degree Mason in the Crescent Lodge, a member of the Knights Templar, Past Master of the Pittsfield F. & A.M., President of the Chamber of Commerce, and a member of the Temple of Mystic Shriners. He was on the Building Committee and a Trustee of the Christian Science Church in Pittsfield.

Harry married Elizabeth Wells and they had four sons.

Brother Sisson died on November 4, 1938 and is buried at Pittsfield Cemetery in Pittsfield,