This paper develops and tests a theoretical model, which assesses the commitment of cities to the concept of open government data (OGD), according to three levels. Level 1, ‘Way of life,’ reflects a high commitment to OGD; Level 2, ‘On the Fence,’ represents either a low or erratic commitment to OGD; Level 3, ‘Lip Service,’ refers to either scarce or no commitment to OGD. These levels draw on four key dimensions: 1) Rhythm; 2) Span of Issues; 3) Disclosure; and 4) Feedback. We empirically examine this theoretical framework using longitudinal mixed-method analysis of the OGD behavior of 16 US cities for a period of four years, using a large novel corpus of municipal OGD metadata, as well as primary qualitative and secondary quantitative indicators. This methodology allows us to represent, for the first time, the evolving OGD commitment — or “OGD heart beat” — of cities.