This chapter explores some critical questions still left unanswered by the racial history of redlining, and contends that the future of studying redlining – its history and its effects – demands bringing 'big data' mapping techniques together with established approaches to social and urban history. Mapping Inequality also overlays the maps on present-day cityscapes to create juxtaposition of past and present urban conditions. Home owners’ loan corporation (HOLC) maps drew on emerging social science research that, in turn, imposed and reinforced a model of racial and ethnic succession and segregation in cities across the country. It staffers bundled the maps with considerable supporting documentation, including tables about lending activity and 'Area Descriptions'. HOLC city surveys represented one of the nation's original big data projects, far surpassing even the neighborhood-level data of the US Census. HOLC agents also used the racial designation of 'risk' and insecurity, by way of their maps, to allocate or deny financing.