Census data, and its underlying geographical framework, is a fundamental resource for social, demographic, and economic applications of GIS. The US and UK censuses have many similarities, but their differences are instructive. This paper examines the constitutional basis of the censuses and the contrasts in the way they are administered. In particular the geographical base used for each census is examined. These issues have a major impact on the products that are made available from each census and the way in which results are disseminated. In particular the US census is taken, and used, for electoral re‐districting to a greater extent than the UK census. The free availability of US data does, however, appear to mitigate against good co‐ordination of census users both in local government and in academe and results in a much more fragmented user community. The paper concludes with an assessment of the similarities and the contrasts between the two censuses.