Dean O. Mehlhaff (June 28, 1927 â April 27, 2016) was an American politician in the state of South Dakota. He was a member of the South Dakota House of Representatives from 1967 to 1976. He served in the United States Army and was a president of the Eureka Chamber of Commerce. He worked in banking and insurance. He died on April 27, 2016, aged 88.