With municipal data portals becoming more commonplace among big cities, the ten Open Government Data Principles principles provide a benchmark for the effective release of government data, possibly serving as a goal for cities to aspire towards achieving in the name of increasing transparency, participation, and innovation. This paper examines the data portals of 32 cities to assess their adherence with the ten principles, and conducts an investigation into what institutional factors may have significant effect on a city’s overall data quality and its adherence to specific principles. It discovers that cities have strong OGD foundations, but that much improvement is still required to achieve full adherence, and that there are no consistent associations between institutional factors and performance on individual data principles. Going forward, it is critical to establish guidelines for what data should be published, and for cities to take greater ownership over data catalog construction.