Objective: Competence to proceed (CTP) is a constitutional protection intended to facilitate fairness and dignity of court proceedings. Researchers have estimated that between 60,000 and 94,000 defendants are evaluated for CTP each year. Yet no research has systematically identified the number of evaluations conducted each year, despite their critical role and many profound implications. We used large-scale, systematic data collection to address this knowledge gap. Hypotheses: Given the siloed nature of the judicial and forensic mental health systems, we anticipated incomplete data and that the number of evaluations would far exceed previous estimates. Method: In September 2019, we used public information requests to solicit CTP evaluation order data from the judiciaries of 50 U.S. states, the District of Columbia, and the Federal Bureau of Prisons. We accepted evaluation proxies, such as evaluations ordered or evaluations filed, from the 2018/2019 calendar/fiscal year. We used Uniform Crime Reporting data to estimate a nationwide evaluation-to-arrest ratio and annual evaluation volume. Results: Twenty-five states provided data. We deemed data from 18 states acceptable while acknowledging that data likely underrepresented actual evaluation volume. By extrapolating data from these 18 states, we estimated a conservative national evaluation-to-arrest ratio of 0.015 (95% confidence interval [−0.007, 0.037]), which suggested that 15 evaluations are conducted per 1,000 arrests each year. Consequently, it seems likely that at least 140,000 evaluations are ordered each year nationwide, with several hundred people referred for evaluations each day. Conclusions: Annual CTP evaluation volume likely far exceeds previous estimates. Transparent data are difficult, if not impossible, to obtain. As a result, researchers, legal and forensic mental health professionals, and policymakers lack the ability to implement informed, constitutionally protected CTP practices. Key implications, research directions, and detailed data infrastructure recommendations are provided.