To estimate the prevalence of adverse childhood experiences (ACEs) among a population-based sample of adults in the United States by their primary source of health care. Debate continues around the effectiveness and implementation of health care-based screening of ACEs. However, it is unclear how the burden of ACEs would be distributed across different sources of health care (ie, what a health system might expect should it implement ACEs screening). Data are from 8 U.S. states that include optional modules for ACEs and health care utilization in their 2019 or 2020 Behavioral Risk Factor Surveillance System survey. The analytic sample includes respondents with completed interviews (n = 45,820). ACEs were categorized into ordinal categories of 0, 1, 2, 3, or ≥4, and the prevalence of ACEs was summarized across 5 sources of health care: (1) employer-based or purchased plan, (2) Medicare, Medicaid, or other state programs, (3) TRICARE, Veterans Affairs, or military (ie, military-related health care), (4) Indian Health Service, or (5) some other source. All estimates were weighted to account for the complex sampling design. Across all health insurance types, at least 60% of individuals reported at least one ACE. The greatest prevalence of patients reporting ≥4 ACEs occurred for military-related health care (21.6%, 95% CI = 18.2-25.5) and Indian Health Service (45.4%, 95% CI = 22.6-70.3). ACEs are extremely common across sources of health care, but some health systems have greater proportions of patients with high ACE exposures. The unique strengths and challenges of specific health care systems need to be integrated into the debate about clinical ACEs screening.