Letters of 1916 is Ireland's first public engagement digital humanities project. Begun in September 2013, it collects, digitises, transcribes, encodes and makes available through its electronic platform epistolary documents written about Ireland between 1 November 1915 and 31 October 1916. This paper analyses the volunteer community associated with the project, inspects the levels of its engagement, studies its interests and motivations and considers how future projects can adapt this investigation into projects addressing community interactions. The basis for this inspection is a user survey carried out in Spring 2016, alongside an analysis of the transcriber community using data on transcriber activity from the beginning of the project in September 2013 to June 2016. The paper argues that the success of a public engagement project lies in the understanding of its community—an understanding derived within a critical framework, inspected through data analysis and communicated through visualisations.