Objective: We sought to identify neurobiological correlates of Melbourne–Sydney rivalry through neuroimaging measures of a key brain region involved in cognitive and emotional regulation. Method: Twenty subjects from each city were recruited from two large neuroimaging databases, and were scanned on a GE Signa 1.5T magnetic resonance imaging scanner. Cortical thickness of the anterior cingulate cortex (ACC) was measured using a tessellated mesh method, after image segmentation. These measures were compared with key sporting, financial and academic variables. Results: Residents of Melbourne had a significantly thicker ACC (p < 0.0001) than Sydney residents, and this difference remained significant when age and intracranial volume were controlled for (p = 0.001). This difference mirrored that in variables measuring wealth, sporting and academic success. Conclusions: The thinner ACC seen in Sydney-siders may reflect the effects of increased stress due to elevated property prices, relative lack of sporting success and other variables. An alternative explanation is that a thinner ACC is the result of increasing cortical refinement and efficiency, and a marker of a more mature city. However, if these findings are a result of latitudinal effects, this may have significant implications for residents of more northern regions of the Australian continent.