Series I. Family Papers includes papers, transcriptions, copies, journals, correspondence, reports, professional and personal writings, compact discs, and floppy disks. Some images may be scattered through this series; they have not been removed if part of the materials in this series. Images of various family members may be found in Series III: Photographic Materials. The materials have been arranged chronologically by primary family member; spouses are generally arranged after children except where otherwise noted. This series has been divided into 15 subseries.

Subseries A. Joseph Coolidge includes copies of correspondence and a memoir from an unknown earlier date about Joseph Coolidge and his life. Subseries B. Thomas Jefferson Coolidge Sr. includes correspondence, clippings, a will, and finding aid information from Baker Library at Harvard University Business School. Subseries C. Mehitable S. A. Coolidge includes transcribed copies of correspondence. Subseries D. Thomas Jefferson Coolidge Jr. includes personal correspondence from Thomas Jefferson Coolidge Jr. to his mother; this correspondence remains intact and in its original order. Additionally, this subseries includes correspondence (copies and transcriptions) from Baker Library and elsewhere, property inventories, and personal memoir manuscripts.

Subseries E. Clara Amory Coolidge includes undated correspondence, clippings, including Clara Amory Coolidge’s obituary, her will, as well as an inventory and appraisal of household furnishings and personal property. Subseries F. Thomas Jefferson Coolidge, III. includes Thomas Jefferson Coolidge III’s personal and professional writings, correspondence, appraisals, clippings, legal documents (wills and trust indentures), and professional memoranda. This subseries is arranged alphabetically; professional memoranda are located separately from the bulk of Thomas Jefferson Coolidge’s materials and have been kept in their original order. Subseries G. Amory Coolidge includes college materials, log books of the Nina and Blue Dolphin yachts, journals, clippings, correspondence, and an inventory upon Amory Coolidge’s death.

Subseries H. William Appleton Coolidge contains information related to William Appleton Coolidge’s art collection, correspondence, legal documents, estate information (including maps and surveys), clippings, appraisals of personal property, personal writings, obituary and tributes. More information regarding William Appleton Coolidge is located in Subseries XI: Catherine Coolidge Lastavica as she was the executor of his estate. Subseries I. John Linzee Coolidge includes a transcribed copy of John Linzee Coolidge’s childhood diary, before his death in 1917. Subseries J. Catherine Hill Kuhn contains correspondence, legal documents, a transcribed diary, and birthday/anniversary related materials. Correspondence from Catherine Hill Kuhn to her daughter Catherine Coolidge Lastavica may be found in Subseries IX: Catherine Coolidge Lastavica.Subseries K. Catherine Coolidge Lastavica contains materials from Catherine Coolidge Lastavica, the Coolidge family papers collection creator. It includes documents pertaining to objects from the Brick House donated to Historic New England, correspondence from various family members, materials pertaining to the Amory family portraits and the creation of The Amory Portraits: A Catalogue of Portraits of Prominent Bostonians, financial and legal documents, documents pertaining to Ravenswood and The Trustees of Reservations, organizations with whom Catherine Coolidge Lastavica was affiliated, professional papers, and research. In addition to textual documents, there are photographs, transparencies, slides, negatives, both cellulose acetate and cellulose nitrate, cartes d’viste, and compact disks in this subseries. There is also material about the controversy over the paternity of Sally Hemings' children.The subseries is arranged alphabetically with donated collections information arranged in accession number order.

Subseries L. Thomas Jefferson Coolidge IV. includes correspondence, legal documents including a will and appraisal, an obituary and tributes. Subseries M. John Linzee Coolidge (Linzee) contains correspondence. Subseries N. Elizabeth Gardner Amory includes both originals and transcribed copies of correspondence with Charles Walter Amory during the Civil War, where he was captured by Confederates. For more information about Elizabeth Gardner Amory see Series IV; she had numerous family histories and genealogical charts created. Subseries O. Other Family Papers contains materials from other descendants of Catherine Coolidge Lastavica. It includes correspondence, diaries, accounts, genealogical information, and appraisals. Of particular interest is a 1791 letter from the Mayor or Paris to an unidentified person, seeking financial aid to build a hospital and a copy of the Account of Charles Walter Amory’s Captivity during the Civil War. This subseries is arranged alphabetically by family member and then chronologically.