In response to the COVID-19 pandemic, jails were advised to reduce facility census, particularly the growing population of those with medical/behavioral health vulnerabilities that increased susceptibility to adverse outcomes. Although jail census decreased across the nation in the initial days to months following pandemic declaration, there are minimal data regarding the health status of those who remained in jail. The current investigation aspired to describe jail census trends before/since the onset of COVID-19 and offer snapshots of temporal changes and context for prevalence estimates of medical/behavioral health conditions in jail detainees from 2019 to 2023. Using a serial cross-sectional design, prescription information for individuals residing in 18 jails across the United States on June 30 of each respective year was extracted and categorized using MediSpan's ontological system to determine prevalence estimates of prescribed agents/products. Although data evidenced an initial 31% census reduction (followed by gradual return to prepandemic rates), prescribing patterns for all major therapeutic drug classes steadily increased, with 10% more individuals prescribed at least one agent in 2023 than 2019. The largest increases were observed for behavioral health agents (e.g., 32.4% of the sample was prescribed psychotropic agents in 2023 compared with 25.7% in 2019). We provide considerations for future investigations.