The Zine Union Catalog (aka ZineCat) is a union catalog dedicated to zines. A union catalog is a resource where libraries can share cataloging and holdings information. ZineCat lets researchers discover zine holdings by searching a single catalog, helps librarians copy catalog records to eliminate duplication of cataloging effort, and facilitates lending across libraries. ZineCat serves educators, researchers, librarians, archivists, and anyone in the general public with an interest in zines. Zines – self-published literature that often features counter cultural, political, and artistic content – are an increasingly important primary resource for humanities, social sciences, and other scholars, but due to the diverse standards and practices among the libraries, archives, and community organizations that collect and maintain them, accessing them through traditional research discovery systems is difficult. The initial prototype was developed by Lauren Kehoe (Faculty Librarian, NYU) and Jenna Freedman (Librarian, Barnard) in their MA Digital Humanities program at the City University of New York Graduate Center using 25 records from three libraries with different metadata schema: MARC, Dublin Core, and a spreadsheet-based standalone schema to a Collective Access catalog. The prototype has grown to include over 31,000 zines from six collections.