As of September 2023, thirty-seven states and Washington, D.C., had adopted the option in the American Rescue Plan Act of 2021 to extend pregnancy Medicaid eligibility to one year postpartum. To inform state initiatives to support this newly covered population, we conducted a representative survey of postpartum people in six states and New York City from January 2021 to March 2022. Compared with respondents who had commercial insurance at the time of childbirth, Medicaid respondents were less likely to have a usual source of care and reported less use of primary, specialty, and dental care in the postpartum year. Depression symptoms and social concerns such as food insecurity, intimate partner violence, and financial strain were significantly higher in the Medicaid population. Rates of anxiety symptoms, delaying or not getting needed care, and unsatisfactory child care were similar in both populations. Our findings suggest that postpartum Medicaid extensions should be coupled with state initiatives to address beneficiaries' health and social needs. National investments in data collection on postpartum people will be critical to support evidence-based policy making to improve maternal health and well-being.