Several countries have made large investments in building historical Geographical Information Systems (GIS) databases containing census and other quantitative statistics over long periods of time. Making good use of these databases requires approaches that explore spatial and temporal change. The authors use a variety of visualization and spatial analysis techniques to explore population change in Ireland during and after the Great Famine of the late 1840s. Importantly, the techniques allow differences over space and time to be explored, thus stressing the diversity between places, rather than making all places appear the same, a common criticism of many statistical approaches. The authors demonstrate the potential of these techniques to explore geographical and temporal variations in large quantitative GIS datasets.