Born in Hadley, Indiana, in 1881, Clark made the journey by narrow-gauge railroad in 1885 with his family to Eagle Rock (now called Idaho Falls). He attended Rose Polytechnic Institute in Terre Haute, Indiana, but cut short his education due to a lung injury during track. He returned to Idaho and engaged in farming, mining, and cattle raising. On October 26, 1905, he married Ethel Salome Peck and they had four children.
Clark became a licensed engineer in 1905 and worked as a civil engineer. His reservoir on the Blackfoot River was purchased by the government and his plan for impounding Lost River was merged into Mackay Dam. After two terms as councilman he served as mayor of Idaho Falls from 1913 to 1915 and again from 1926 to 1936. During this term, the city built the Municipal Hydroelectric Plant No. 1.
Clark's interest turned to Idaho mines until he was again elected Mayor of Idaho Falls in 1927 and served in that office until his inauguration as Governor on January 4, 1937. During his tenure, a state tuberculosis hospital was authorized, a judicious pardon and parole system was installed, and junior college districts were installed. He left office January 2, 1939, and returned to Idaho Falls and his private interests.Clark's younger brother, Chase Clark, also served as governor of Idaho.
Clarke died September 21, 1943, of lung cancer in Idaho Falls. He is interred at Rose Hill Cemetery, Idaho Falls, Bonneville County, Idaho USA.
He was a member of Trinity United Methodist Church in Idaho Falls.