Born in Watertown, Connecticut, Fenn moved with his parents to Niagara County, New York, in 1824.
He attended the public schools and moved in 1841 to Jackson County, Iowa, where he held several local offices. Fenn moved to California in 1850 and engaged in mining and ranching, studied law, and was admitted to the bar in 1862 and commenced practice in that part of Washington Territory which became a part of the Territory of Idaho upon its organization in 1863. He also engaged in mining and served as member of the Idaho Territorial Council from 1864 to 1867. Fenn served as district attorney for the first judicial district in 1869 and was elected in 1872 as a member of the Territorial House of Representatives and served as its speaker.[1]
He engaged in agricultural pursuits and successfully contested as a Democrat the election of Thomas W. Bennett to the forty-fourth Congress. Fenn was reelected to the forty-fifth Congress and served from June 23, 1876, to March 3, 1879. He was not a candidate for renomination in 1878 and continued his former pursuits until July 1891. Fenn's mind weakened in his later years and he died in the insane asylum in Blackfoot, Idaho, on December 8, 1892.[2]
^Curtis, George H.; Wells, Merle (1944). "The Political Founders of Idaho". Twenty-Seventh Biennial Report of the Secretary of State of Idaho. pp. 59–77.