Digital archives are the preferred means for open access to research data. They play essential roles in knowledge infrastructures—robust networks of people, artifacts, and institutions—but little is known about how they mediate information exchange between stakeholders. We open the “black box” of data archives by studying DANS, the Data Archiving and Networked Services institute of The Netherlands, which manages 50+ years of data from the social sciences, humanities, and other domains. Our interviews, weblogs, ethnography, and document analyses reveal that a few large contributors provide a steady flow of content, but most are academic researchers who submit data sets infrequently and often restrict access to their files. Consumers are a diverse group that overlaps minimally with contributors. Archivists devote about half their time to aiding contributors with curation processes and half to assisting consumers. Given the diversity and infrequency of usage, human assistance in curation and search remains essential. DANS’ knowledge infrastructure encompasses public and private stake- holders who contribute, consume, harvest, and serve their data—many of whom did not exist at the time the DANS collections originated—reinforcing the need for continu- ous investment in digital data archives as their communi- ties, technologies, and services evolve.