There is a growing trend across the social sciences to engage with archives. Within Human Geography this has stimulated a debate about the nature of archives, including moving from considering ‘archive as source’ to ‘archive as subject’. We build on and extend this thinking, suggesting that an even more active appreciation of the dynamic nature of relationships between researchers, owners of records, and archival material is needed. This paper draws on an interdisciplinary study of voluntary action and welfare provision in England in the 1940s and 2010s to highlight how the different iterative processes involved in collaborative archival research are part of what we call co-curation. Co-curation involves the negotiated identification, selection, preparation, and interpretation of archival materials. This has implications for both research processes and outcomes.