 Born in Huron, South Dakota, Viken earned a Bachelor of Arts degree from the University of South Dakota in May 1974 and a Juris Doctor from the University of South Dakota School of Law in May 1977.He did not take the bar exam as he was admitted to the South Dakota bar under diploma privilege.From 1977 until 1981, Viken served as an Assistant United States Attorney for the District of South Dakota and in 1981 became the Acting United States Attorney for the District of South Dakota.