At age 16, he enlisted in the Sixth Ohio Volunteer Cavalry during the American Civil War participating in several battles including Antietam and Gettysburg.

After the war, he spent a year in high school and then entered the Bellevue Hospital Medical College in New York City.

The act established a commission which included a psychiatrist president and two lay members and was charged to be responsible for the state mental hospitals.

MacDonald was appointed as the president and held the position until 1896 when he resigned in protest of the commission to carry out its responsibilities which were seen by the state hospital superintendents as a threat to their autonomy.

MacDonald found the prisoner sane and attended Czolgosz’s execution in the electric chair.

In 1906, MacDonald purchased a private mental hospital, Falkirk Sanatorium, in Central Valley, New York, which he operated for many years.