The Hidden Collections Initiative for Pennsylvania Small Archival Repositories (HCI-PSAR) was a project of the Historical Society of Pennsylvania funded by the Andrew W. Mellon Foundation. Its goal was to make better known and more accessible the largely hidden collections at small archival repositories in the five-county Philadelphia region. These included volunteer-run historical institutions, museums, fraternal and ethnic organizations, community groups, churches, clubs, and other non-profit organizations with important archival collections.

Hundreds of small archival repositories in the five-county Philadelphia region hold thousands of individual collections documenting a wide range of topics and geographic areas. Private, non-profit organizations with a history-based mission or that have historically significant archival collections, that agree to make their archives available to the public, and that do not employ a full-time, professionally trained archivist were eligible for participation in the project.

Project staff identified small archival repositories in the Philadelphia area, surveyed and assessed their archival collections, and created summary finding aids to these collections. The finding aids were made publicly accessible in an online database developed by the Philadelphia Area Consortium of Special Collections Libraries (PACSCL). Within this single online resource, researchers may search collections held at a wide range of Philadelphia-area archival repositories, from the smallest all-volunteer organizations to the largest professional institutions.

Project staff also served as a resource for local small repositories, offering training programs, advice, and assistance with issues of archival management and collections stewardship.

HCI-PSAR was a multi-phase project that began in 2011. During Phases I and II (July 2011 to October 2014), project staff visited 130 small repositories in the five-county Philadelphia region and surveyed and assessed over 1,100 individual archival collections totaling more than 12,000 linear feet of materials.

Phase III began in November 2014 and concluded in April 2016. In addition to surveying remaining small historical organizations in the five-county Philadelphia region, Phase III expanded the scope of the project to include more types of repositories with significant archival holdings, such as churches, fraternal and ethnic organizations, and community groups. Additionally, project staff offered training programs, fostered information-sharing opportunities, and worked to create sustainable advances in professionalism and capacity among small archives in the region. Project staff also promoted HCI-PSAR as a national model, presenting on the project at professional conferences and working with archivists in other parts of the country to develop small repository initiatives in their areas.

Finding aids created through this project were added on an ongoing basis to the PACSCL finding aid website. There is also an interactive map showing locations of the repositories visited. Project staff highlight interesting repositories visited and important collections uncovered on the project's Archival Adventures in Small Repositories blog, as well as on Facebook and Twitter.