Simak was born in Millville, Wisconsin to parent's John Lewis and Margaret (Wiseman) Simak. He married Agnes Kuchenberg on April 13, 1929. They had two children, Scott and Shelley. Simak attended the University of Wisconsin–Madison. He later worked at various newspapers in the Midwest. He began to work with the "Minneapolis Star and Tribune" (in Minneapolis, Minnesota). This went from 1939 to his retirement in 1976. 