This article explores the impact that a series of Archives Unleashed datathon events have had on community engagement both within the web archiving field, and more specifically, on the professional practices of attendees. We present results from surveyed datathon participants, in addition to related evidence from our events, to discuss how our participants saw the datathons as dramatically impacting both their professional practices as well as the broader web archiving community. Drawing on and adapting two leading community engagement models, we combine them to introduce a new understanding of how to build and engage users in an open-source digital humanities project. Our model illustrates both the activities undertaken by our project as well as the related impact they have on the field. The model can be broadly applied to other digital humanities projects seeking to engage their communities.