Series I. General correspondence
Subseries Ia. A chronological arrangement of general correspondence
Subseries Ib. Correspondence of a particular topic arranged chronologically
Series II. Family correspondence
Boxes: 4-17, F.10
Family correspondence of ten or more letters arranged chronologically. Family members include Hendrik's immediate family of parents, aunts, uncles, and two sons, and Eliza Bowditch van Loon's parents, her siblings, and cousins. Also postcards to and from family members. Major correspondence of ten or more letters between those friends with whom Hendrik maintained a regular correspondence is included in this series. Also included is correspondence between his second wife, Helen Criswell van Loon, and his third wife, Frances Ames Goodrich. This material is listed alphabetically by correspondent and arranged chronologically.
Series III. Major correspondents
Boxes: 17, F. 11-19
Major correspondents include those individuals who were considered important personalities in the 1900's-1940's, with whom Hendrik wrote irregularly (less than ten letters). This material is listed alphabetically and includes number of letters and inclusive dates. Also included in this series are draft copies of correspondence and microfilmed correspondence.
Series IV. Manuscript material
Manuscript material includes carbons, drafts, and typescripts for articles, books, broadcasts, lectures, serials, and Hendrik Willem van Loon's thesis. Book material is arranged alphabetically by title. Articles, broadcasts, lectures, serials, and the thesis are arranged separately in chronological order when possible. The letters N/A were used when no title was available.
Series V. Printed material
Printed material consists mainly of English and foreign translations of various van Loon books: articles about van Loon in both foreign and American papers and magazines; reviews; promotional book material; cruise ship pamphlets; copies of illustrations that appeared in various newspapers and magazines; and miscellaneous clippings.
Series VI. Illustrative material
Illustrative material includes the illustrations made for many van Loon books arranged by book title; sketches for unfinished books; sketchbooks; illustrated stories and unpublished material; illustrated folders, envelopes, and menus; small pen-and-ink and watercolor sketches either mounted or on mats; ornate matted sketches; book jackets; many miscellaneous sketches; and portraits of van Loon by other artists.
Series VII. Memorabilia
Boxes: 53-62 Map Case Special locations
Subseries VIIa. Includes scrapbooks, guestbooks, photograph albums and photographs, notebooks, diaries, passports, pamphlets, certificates, diplomas, phonograph records, games, puzzles, and miscellaneous.subseries
Subseries VIIb. Collected memorabilia includes various miscellaneous documents, volumes, and reprints collected by van Loon.
Series VIII. Papers of Helen Criswell "Jimmie" van Loon
Papers of Helen Criswell "Jimmie" van Loon include an original play, diaries, "Mad Hatter Mutterings," and other miscellaneous material.
Series IX. Papers of Gerard Willem van Loon
Papers of Gerard Willem van Loon includes drafts and photos for his biography about Hendrik Willem van Loon, and correspondence pertaining to his father and the manuscript.