This volume documents the capstone event to the seven-year Cataloging Hidden Special Collections and Archives program, funded by The Andrew W. Mellon Foundation. The two-day symposium and unconference brought together more than 180 participants, including many past and current grant recipients. In the proceedings, more than 20 symposium presenters examine inter-institutional collaboration, student and faculty involvement, cataloging, arrangement and description, audiovisual collections, science collections, and outreach.