Stewart was born on January 11, 1916, in rural Poweshiek County, Iowa to Lewis and Mary Enerson Buchenau. He was raised on the family farm and graduated from Grinnell High School. During World War II he served with the U.S. Navy in the Atlantic Theatre. On November 18, 1944, he was married to Frances Allen in Lynnville, Iowa. The couple farmed near Prairie City and in 1966 they moved to a farm near Grinnell. He moved into Grinnell in 1983 but never retired from farming. His life was devoted to farming and caring for his livestock. Survivors include his son, Steven (Amy) Buchenau of Grinnell; and one grandson, Lee A. Buchenau of Grinnell. He was preceded in death by his parents; his wife; one sister, Flora Buchenau; and one brother, Laverne Buchenau.