The US census is characterised, among other features, by the importance it gives, to this day, to race. There is an ongoing debate on the use of racial categories to underpin affirmative action policies, but their presence in the census is little discussed. This tends either to mask the functions of racial and ethnic categories in the pre‐civil rights era or to lead to consideration of such categories as a mere residue of historical discrimination. Yet it would be unfortunate to write a history of such census categories that reduces them to these two functions: to identify, first, groups of non‐European origin and then ‘new immigrants’ subject to official discrimination, and later their supposed descendents in order to include them within the scope of compensatory policies. Such an approach would elide the more complex and still largely neglected history of the social construction of ethnic and racial categories. This article examines several cases in which groups mobilised to demand that government agencies should take account of their existence in a different way, in a context where no material advantage was at stake. In so doing, it historicises the statistical categories of race and ethnicity, which cannot be understood solely by reference to their current usage.