PopMedNet™ (PMN) is an open-source application used to facilitate multi-site health data networks. PMN uses a distributed network design that enables data holders to retain full control of their data. PMN enables investigators to send questions to data holders for review and response, rather than assembling patient records in a centralized repository. Since its inception 10 years ago, PMN has grown to a mature, full-featured open source application that powers several distributed health data networks.