YouthMappers is a global network of student chapters actively engaged in collaborative mapping efforts, such as OpenStreetMap mapathons. Many questions have been raised about the impact of mapathons on open map data and on the participating mappers. For example, how can the social gathering and event format encourage productivity and quality, while also contributing to community building? Because YouthMappers chapters regularly host mapathons, there are frequent opportunities to investigate the impact of mapathons. In this paper, three universities involved in the YouthMappers network, located in Europe, North America and Africa, describe how mapathons are conducted at their respective universities. Incorporating mapathons into the curriculum encourages students to contribute much-needed open geospatial data for humanitarian projects. At the same time, students get practical experience in data capturing with open source tools and awareness is raised of humanitarian challenges in other parts of the world, thus nurturing socially engaged citizens for the future. The experiences at the three universities are diverse and richly contextual to the specific character of the campus and its students. These differences underscore the challenge of a common means to formally assess the impact of such events in general. Based on this exploratory research, three themes for assessing the impact of mapathons are proposed: the volume and quality of open geographic data produced during mapathons; the social and personal growth of the students attending the mapathons; and the changes in university programs and curricula introduced as a result of the mapathons.