Barzilla Worth Clark was born in Hadley, Indiana, December 22, 1881. He was the son of Joseph Addison and Eunice (Hadley) Clark who were among the Hoosier state's Quaker settlers. In 1885 the Clarks arrived in Eagle Rock--now called Idaho Falls--having made the trip from Indiana via narrow gauge railroad. In addition to attending public schools in Idaho Falls, Barzilla returned to Indiana where he attended Rose Polytechnic Institute in Terre Haute. When ill health forced him to cut short his education, he returned to Idaho and engaged in farming, mining and cattle raising.

In 1905 he married Ethel S. Peck, of Idaho Falls. They had four children, 3 daughters and a son. He early became interested in conservation and the development of natural resources, particularly irrigation and hydroelectric projects. His reservoir at the headwaters of the Blackfoot River was later purchased by the government and his plan for impounding Lost River was merged into the Mackay dam.

After serving two terms as councilman, he was elected mayor of Idaho Falls in 1913. During this term the city built the municipal hydroelectric plant no. 1, located just below the Broadway Bridge. Following a period of interest in central Idaho mines, he was again elected mayor in 1927 and continued in that office until he was inaugurated as governor of Idaho in January 1937. At the expiration of his single term as governor in 1939 he returned to Idaho Falls and the development of his personal interests there.

On September 21, 1943, Barzilla W. Clark died of lung cancer in Idaho Falls.