When Walter Frank Mittendorf was born on 9 January 1918, in Owensville, Gasconade, Missouri, United States, his father, William Henry Mittendorf, was 45 and his mother, Louisa Ernestine Guese, was 26. He married Thedora Bell Hayden on 26 April 1941, in Carbon, Montana, United States. They were the parents of at least 1 son. He lived in Brush Creek Township, Gasconade, Missouri, United States for about 10 years and Antelope, Sierra, California, United States in 1997. He registered for military service in 1943. He died on 30 October 1995, in Sacramento, California, United States, at the age of 77, and was buried in Sacramento, Sacramento, California, United States.