Born in Albany County, New York, April 9, 1818. His early life was passed on his father’s farm and his education begun at the Academy of Schoharie Court House. He entered Union College, graduating in 1844. Later he studied theology in New York City and Covington, Kentucky, graduating in 1846. Mr. Denison came to Crawford County, Iowa, in 1856, as agent for the Providence Western Land Company which, through him, acquired 21,000 acres of land in Crawford, 3,000 in Harrison and 1,000 acres each in Shelby and Pottawattamie counties. He laid out the town of Denison and for many years worked for its interests in securing the county-seat and railroad connections. He was the Founder of the county-seat of Crawford County. He organized the Baptist church during the first year and was its pastor until 1863. He was active in the promotion of education and the establishment of schools and for twenty years was untiring in all good work to develop the new country where he had settled. In politics he was a Republican and in 1859 was elected Representative for the district composed of the counties of Crawford, Monona, Carroll and Greene, serving in the regular session of the Eighth General Assembly and the war session of May, 1861.