Andrew A. Cour
Source: Rogers Park Directory, 1919, page 19.
When the Chicago Public Library was asked about the meaning of MGDO they replied:
It is likely that MGDO is an abbreviation of Medical Gymnast; Doctor of Osteopathy.
Andrew A. Cour is listed under 'Osteopathic Physicians in the July 1919 Chicago Classified Directory. In the January 1913 issue of The Journal of Osteopathy, page 41 (page 19 of the pdf) he is mentioned as having given a talk to the Chicago Osteopathic Association in 1912 on medical gymnastics:
The text reads:
A very interesting talk was given by Dr. Andrew A. Cour on Medical Gymnastics. The able presentation of this subject awakened an interest in all those present. The instructions of giving medical exercises for the purpose of overcoming deviations and maintaining correction were very helpful. A vote of thanks was tendered Dr. Cour for his very instructive lecture.