Politicians and policymakers have long dreamed of creating a national system of electronic health records (EHRs) that would radically transform the delivery of health care. The theoretical advantages of EHRs are tantalizing: among other things, they could reduce medical errors, improve care coordination, limit duplicative testing, and help uncover new public health strategies. Over the past decade, the United States health care system has made progress toward realizing this vision. Until relatively recently, patients’ medical histories were typically transcribed on physical notepads and stored in filing cabinets, which were often difficult for providers and patients to access or understand. Today, by contrast, the vast majority of health care providers utilize EHRs, a sea change that is largely attributable to federal policy. Since this transition, there have been occasional glimpses of the benefits of EHRs. For instance, the pediatrician who brought the water crisis in Flint, Michigan to public attention did so by utilizing data from EHRs. The data from EHRs led to discovery of abuses of adolescent inmates at Rikers Island, and helped to form the basis for a Department of Justice civil rights investigation. Nevertheless, today, despite billions of dollars in investments, thousands of pages of regulations, and countless hours spent implementing and adapting to new technology and requirements, EHRs have failed to live up to their promise. Studies exploring the impacts of EHRs have had mixed results, at most finding modest incremental improvements. At the same time, glitches in EHR software and user errors have led to a rash of reported medical errors and even several patient deaths. EHRs have also created onerous administrative burdens for health care providers, which interfere with patient care and have increased rates of burnout among clinicians. President Obama himself specifically cited EHRs as the main disappointment of his administration’s health care policy, saying, “[w]e put a big slug of money to encouraging everyone to digitalize … [a]nd it’s proven to be harder than we expected.” Perhaps the most important way in which EHRs have failed to live up to their promise is that they are not “interoperable”: they cannot be easily exchanged across systems. Many of the theoretical benefits of EHRs depend on their being interoperable. For instance, an interoperable EHR system could reduce medical errors by enabling emergency room doctors admitting an unconscious patient to quickly look up the patient’s medical history and current medications. It could increase care coordination by allowing multiple providers working in different health systems, yet caring for a single patient, to share notes and records. This would be especially beneficial for economically disadvantaged patients, whose care tends to be fragmented across multiple providers. These advantages rely on being able to easily exchange data across health systems. Without interoperability, many of the benefits of EHRs cannot be realized. Thus, even though the majority of health care providers now utilize EHRs, patients’ health information is still siloed within individual health systems or within specific types of EHR technology. Instead of being stuck in physical filing cabinets, patients’ health records are now often stuck in electronic ones. Although there are both technical and regulatory barriers to interoperability, conflicting financial incentives arguably pose the greatest challenge. EHR vendors and health care systems have little to gain—and much to lose—by making EHRs interoperable. Until quite recently, however, both Congress and federal regulators had done little to directly address this incentive problem. This article explores why, despite tremendous investment by both the public and private sectors over many years, we still do not have an interoperable EHR system, and whether the promise of EHRs can still be salvaged. Part I describes the barriers to ensuring interoperability, focusing on health care organizations’ conflicting incentives. Part II reviews the history of federal efforts to promote EHRs and explores why they failed to achieve interoperability. Part III discusses recently proposed regulations designed to address this problem, what they accomplish, and some areas of concern.