Sjaastad graduated from the U.S. Naval Academy in 1952, and retired as a colonel in the Air Force in 1974. He attended the Princeton Graduate School and earned a Ph.D. in civil engineering in 1963. His military career included a tour in Vietnam and working as chief of structural engineering at the Air Force Academy.
In 1974, he became deputy director of the Colorado Department of Natural Resources. After a short career there, he opened a private law practice (having graduated from Denver University Law School in 1973) and was an attorney for 25 years. Owner of a ranch in Colorado, he also was a dedicated land conservationist for many years.
Sjaastad is survived by Barbara, his wife of 57 years; three children; and five grandchildren.
Graduate memorials are prepared by the APGA.