HMML Authority File (HAF) is an open access database that shares lists of authorities used in HMML’s Reading Room and Museum. Metadata in HAF is submitted to the Library of Congress’s Name Authority Cooperative Program (NACO) as part of HMML’s partnership in the Program for Cooperative Cataloging. The HMML Authority File is part of the Resources for Description of Manuscripts from Understudied Christian and Islamic Traditions project funded by the National Endowment for the Humanities that will help build the scholarly infrastructure to create access to endangered manuscripts digitized by the Hill Museum & Manuscript Library. HAF is a living authority file improved over time. Some authorities may begin as sparse records but grow in detail as additional information is uncovered.