‘World city research’ has always sought to identify links between the expansion of the world economy and social marginalisation. Changes in the division of international labour have provided the main explanatory insights. I believe that, given the financialised nature of the global economy, other theoretical instruments can be employed, such as the concept of ‘financial exclusion’ for example. Because of the way they have manifested in Chicago, the causes and consequences of the ‘mortgage meltdown’ are able to give us a chance to explain how financialisation has produced social marginalisation. Firstly I explain how the ‘meltdown’ of the secondary mortgage market has contributed to financial exclusion and then, in the local context, I analyse the relationships between financial exclusion and old and new patterns of marginalisation resulting from financialisation.