Major general
Major generals of the staff proliferated after 1912, when the Quartermaster Corps was created under a Quartermaster General bearing the temporary rank of major general. The Surgeon General reached that rank in 1915 when William C. Gorgas was appointed to that post and promoted to major general in the Medical Department to reward his service during the construction of the Panama Canal. The Chief of Coast Artillery became a major general of the staff in 1916. Finally, every other chief of a staff corps, department, or bureau was elevated to major general on October 6, 1917.