Series III. Essex Institute Papers contains records pertaining to Rantoul's personal and professional affiliation with the Essex Institute, from his early days as a member and researcher through his years as President and later as nominal head of the organization. The series contains a wealth of correspondence addressed both to and from Rantoul as he addressed research requests, sought information or materials from others, and liaised with libraries and historical societies. Additionally, the series documents a number of the pamphlets and essays that Rantoul published as a result of his association with the Essex Institute, including notable works on the Woodbury family genealogy and the first cotton mill in the United States. Supplementing these is a folder of reports and speeches that Rantoul gave on various historical and current topics based on his research at the Institute, some of which were later reproduced in local newspapers or sent to other historians. Finally, this series contains a folder of transcriptions copied either by or for Rantoul from Essex Institute materials and other related historical records for the purposes of research. These handwritten or typed copies clearly address a number of different research interest and projects, but are all undated and detached from their original context.