Documenting and measuring mortality in correctional facilities is essential for understanding the health consequences of incarceration, identifying preventable deaths, and informing policy interventions. We undertook a compilation of publicly available mortality records in state-operated correctional facilities, encompassing data gathered from administrative, nonprofit, and public records. The Harmonized Carceral Mortality Database (HCMD) standardizes decedent characteristics, facility identifiers, locations, dates of death, and causes of death to enable epidemiological analyses of mortality in U.S. prisons, outside of federal reporting. At the time of writing, the HCMD includes 49,682 deaths from at least 1,089 prisons in 50 states, spanning 1996-2024, with regular updates annually. The HCMD supports carceral health research across a range of disciplines from environmental health to sociology to criminology and supports use beyond the scientific community, including journalists, lawyers, and community-based organizers.