Coleman was born in Richfield Springs, New York in 1827 to Hamilton and Nancy Coleman. He received a law degree from the University of Louisville Law School in 1849. Coleman then moved to Missouri and went into farming. In 1855 he started the "Valley Farmer" newspaper. As a result of the newspaper, Coleman became an important person in the Missouri farming community, which helped him become a member of the Missouri House of Representatives. Coleman’s newspaper stopped due to the American Civil War, but three years after the war he started the "Coleman’s Rural World". His career in politics continued when he was made the Lieutenant Governor of Missouri from 1875 to 1877. During that time he worked to make United States Department of Agriculture a cabinet-level department. Under the administration of President Grover Cleveland, he served as its first Secretary. His position as Secretary of Agriculture was never confirmed by the United States Senate.