Litchfield Historical Society institutional records consists of records created by the Society or relate to it and documents all aspects of its history. The collection includes correspondence, minutes, architectural records and drawings, ledgers and other accounting records, scrapbooks, and other records. The collection consists of ten series.

Series 1. Board of trustee records (1884-2022) contains minutes, correspondence, board resolutions, officer records, legal and financial records, annual reports, and other materials produced by or for the board of trustees. Records printed for the board or relate to their activites; Series 3 contains documentation related to other publications of the Society.

Series 2. Building and site records (1876-2020) contains records relating the various buildings and sites the Society previously or presently owned, including Noyes Memorial Building (the main administrative building, which also includes the library, archives, and museum), the Tapping Reeve House and Litchfield Law School, and the Pamela Cunningham Copeland Curatorial Center. The records include abundant documentation of renovations and reinterpretations associated with the structures.

Series 3. Major projects (1910-1929) consists of documentation relating to exhibitions, publications of the Society, education programs, accreditation by the American Association of Museums, the online database The Ledger, and several video and internet projects. Activities related to exhibitions, such as catalogues, fundraising and grants, and public programs, will be found in subseries related to the specific exhibition.

Series 4. Finanical records (1884-2020) include correspondence, bills and receipts, account books, capital campaign and fundraising activities materials, analyses and reports, and other materials. The bills and receipts, arranged alphabetically, include a wide range of vendors from the 1890s to the 1990s are of particular interest. Reports of the treasurer are found in Series 1.

Series 5. Membership (1884-2007) includes member lists and dues records, correspondence, brochures, membership cards, and related materials.

Series 6. Office/administrative materials (1884-2023) include records related to the general management of the Society, including the administrative duties of the directors, the curation of the museum collections, and the administration of the library and archival collections. The director's files are especially useful in documenting the activities of the Society from the mid-twentieth century forward. Records in the Curatorial subseries document the Society's holdings beginning with the late 1800s. Additional museum and archival accession records are maintained separately from this collection.

Series 7. Personnel (1979-2014) includes documentation related to job searches, personnel policies, funding for staff development, and similar activities.

Series 8. Public events and programming (1895-2008) consists almost entirely of publicity materials for events offered to the general public. Documentation of programs and activities, such as symposia offered in conjunction with exhibitions and fundraising events and dinners, will be found with the specific programs and activities in other series. Events and proramming in this series are generally stand-alone activities, such as lectures on topic unrelated to exhibitions; activities the Society may have a role in, such as Borough Days; and summer programs for children.

Series 9. Marketing and publicity materials (1901-2008) consist of descriptive brochures and postcards, newsletters, scrapbooks of clippings, loose clippings, and other items that generally document the activities of the Society that appeared for public perusal.

Series 10. Guest registers (1893-2019) document visitors to the various buildings, including the museum and Society, Tapping Reeve House and Litchfield Law School, and defunct associations.

Series 11. Litchfield Scientific Association (1903-1925). Founded in 1903, the mission of the Litchfield Scientific Association was to promote an interest in scientific subjects and to collect a museum illustrative of natural history in Litchfield County. It merged with the Society in 1919. The records include a small group of programs and correspondence, two scrapbooks, and a visitors book.