The fonds consists of correspondence that spans the years 1898 to 1978, with the bulk of the material from 1930 to 1965. Fonds also includes transcripts, press clippings, notebooks, reports, minutes and publications. The fonds reflects the overlap of personal and corporate interests in MacMillan's life. Correspondence regarding UBC, Canadian and foreign business and personal contacts, his relationship with community groups and memberships he held, as well as his family history is included.