The advantages of using digital boundary data as part of the process of analysing and visualising census data are well known. In many countries census data and their associated boundaries are now published as an integrated digital product. To truly understand the present, however, we must also understand the past and the changes that have led us to the present. Several European countries and regions have, therefore, created GISes of their changing administrative boundaries as a first stage in fully understanding the spatial and temporal complexities of long-term socio-economic change. Many others have plans to do so. In June 2000 a European Science Foundation funded workshop was held in Florence organised by Drs H Southall, M Goerke, and G Thorvaldsen. The meeting's title was "Mapping Europe's historic boundaries and borders: An exploratory workshop" (Southall et al. 2000). The meeting included a session on "Constructing historic boundary GISes" in which representatives of projects from various countries and regions reported on how their project had approached the problem of creating time-variant GISes of changing socio-economic units. This paper examines the different approaches to creating temporal GISes that are described in the literature and compares this to the actual methods used by these European projects.