We designed, developed, and studied a visualization, WPHPVis, to support exploration of the Women's Print History Project (WPHP) data. WPHP are manually-collecting a bibliography that spans the years 1700 to 1836 recording information about books in which women have been involved through a number of roles including as authors, editors, translators, publishers, printers and booksellers. By working directly with WPHP experts to focus on their understanding, and their research practices and needs, we co-designed WPHPVis using interactive construction of network links to support exploration of their data. Through our qualitative study with both experts and non-experts, we learned about how the tool supported the WPHP experts' research practices as well as about how to improve overall interactive experience. We conclude by discussing the importance of representing missing data, the advantages of striking a balance between visualization structure and explorability, and the opportunities enabled by co-design with domain experts.