[6] McDonald served four years in the United States Navy during World War II[7] and attained the rank of lieutenant.

He also served as a consultant on buildings and management for libraries and museums across the United States and as far away as Santiago, Chile.

[10] McDonald served as president (1971–72) and, while on leave of absence from UConn, executive director (1974–76) of the Association of Research Libraries (ARL).

[8] McDonald was an avid bird watcher and conservationist, serving on the boards of Joshua's Tract Conservation and Historic Trust and the Connecticut Ornithological Society, among other organizations.

[7] The John P. McDonald Reading Room located in the Thomas J. Dodd Research Center was named in his honor.