At the Army Medical Library, Garrison was assigned to index medical literature. He worked closely with John Shaw Billings on this project. He helped create and compile the Index-Catalogue of the Library of the Surgeon General's Office. His editorial experience includes: Index Medicus: Associate Editor 1903-1912; Editor 1912-1927; Associate Editor, Quarterly Cumulative Index Medicus 1927-1929.

He wrote the first comprehensive treatise on the history of medicine and "gained recognition as the foremost American authority on the subject" (Dict. of American Biography). Garrison prepared plans and collected material for the history of the U.S. Medical Department during World War I. In 1925, he was appointed consulting librarian to the New York Academy of Medicine.