This series contains the business records of the staff, which produced the . It includes correspondence with Macmillan (the publisher of the ), with sponsoring organizations, and with subscribers. Also present are financial records, including bills and invoices, checkbook ledgers, account books, and information on staff and salaries. Files of press notices, reviews of the , and a scrapbook of press clippings are also present in this series.

This series contains an assemblage of files used in planning the . First is a set of lists of suggested topics, arranged by broad subject field. These lists were circulated to eminent authorities in each field for comment. Each file consists of the lists, comments by the outside authorities, and related correspondence. Second there is a set, also filed by broad subject area, of outlines and abstracts of articles, including enumerations of suggested word lengths for each article. This is followed by a series of Memoranda to Authors, filed alphabetically by subject, giving the scope for each suggested article or series of related articles. A set of miscellaneous files relating to these lists and outlines follows. The remainder of the series consists of the card files used in the preparation of the . First, a set of Topic Cards with brief summaries of articles, suggested word lengths, and often notes on who suggested the topic, and possible authors for the articles. Then there is a set of Abstract Cards (A through L only), which mainly seem to include suggested authors for the articles, although some outlines and suggested word lengths are also present. Finally is a set of Biography Cards, which are identical to Topic Cards except that they treat personal name subjects.

This series contains the original manuscripts and edited drafts of the articles of the Encyclopaedia. Often included are notes on background information and statistics, as well as slips for sources consulted at the New York Public Library in the course of the factual checking done by the staff. Occasionally correspondence relating to the article will be found in these files, but most correspondence is filed in the next series.