He was the sixth of August Valentine and Katarina (née Schmitberger) Menninger's eight children and their youngest son.
[5] Menninger married Florence Vesta Knisley, on January 15, 1885 and together they had three children: Karl, Edwin,[6] and William.
He was taken on as a junior partner by Henry Roby, who influenced his pursuit of additional medical training focused on internal medicine and metabolic issues.
[4] In 1919, upon completion of his son Karl's medical training at the Boston Psychopathic Hospital, the two formed a professional partnership and opened the Menninger Clinic.
[7] It eventually evolved into the Menninger Foundation, a national institution for the study and care of people suffering from mental illnesses.